compression/index.html at main · stwrt/compression · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
<!doctype html><html lang="en">
 <head>
  <meta content="text/html; charset=utf-8" http-equiv="Content-Type">
  <title>Compression Streams</title>
  <meta content="width=device-width, initial-scale=1, shrink-to-fit=no" name="viewport">
  <link href="https://www.w3.org/StyleSheets/TR/2021/cg-draft" rel="stylesheet">
  <meta content="Bikeshed version fe8c230, updated Wed Aug 10 08:18:38 2022 -0700" name="generator">
  <link href="https://wicg.github.io/compression/" rel="canonical">
<style>/* style-autolinks */

.css.css, .property.property, .descriptor.descriptor {
    color: var(--a-normal-text);
    font-size: inherit;
    font-family: inherit;
}
.css::before, .property::before, .descriptor::before {
    content: "‘";
}
.css::after, .property::after, .descriptor::after {
    content: "’";
}
.property, .descriptor {
    /* Don't wrap property and descriptor names */
    white-space: nowrap;
}
.type { /* CSS value <type> */
    font-style: italic;
}
pre .property::before, pre .property::after {
    content: "";
}
[data-link-type="property"]::before,
[data-link-type="propdesc"]::before,
[data-link-type="descriptor"]::before,
[data-link-type="value"]::before,
[data-link-type="function"]::before,
[data-link-type="at-rule"]::before,
[data-link-type="selector"]::before,
[data-link-type="maybe"]::before {
    content: "‘";
}
[data-link-type="property"]::after,
[data-link-type="propdesc"]::after,
[data-link-type="descriptor"]::after,
[data-link-type="value"]::after,
[data-link-type="function"]::after,
[data-link-type="at-rule"]::after,
[data-link-type="selector"]::after,
[data-link-type="maybe"]::after {
    content: "’";
}

[data-link-type].production::before,
[data-link-type].production::after,
.prod [data-link-type]::before,
.prod [data-link-type]::after {
    content: "";
}

[data-link-type=element],
[data-link-type=element-attr] {
    font-family: Menlo, Consolas, "DejaVu Sans Mono", monospace;
    font-size: .9em;
}
[data-link-type=element]::before { content: "<" }
[data-link-type=element]::after  { content: ">" }

[data-link-type=biblio] {
    white-space: pre;
}</style>
<style>/* style-colors */

/* Any --*-text not paired with a --*-bg is assumed to have a transparent bg */
:root {
    color-scheme: light dark;

    --text: black;
    --bg: white;

    --unofficial-watermark: url(https://www.w3.org/StyleSheets/TR/2016/logos/UD-watermark);

    --logo-bg: #1a5e9a;
    --logo-active-bg: #c00;
    --logo-text: white;

    --tocnav-normal-text: #707070;
    --tocnav-normal-bg: var(--bg);
    --tocnav-hover-text: var(--tocnav-normal-text);
    --tocnav-hover-bg: #f8f8f8;
    --tocnav-active-text: #c00;
    --tocnav-active-bg: var(--tocnav-normal-bg);

    --tocsidebar-text: var(--text);
    --tocsidebar-bg: #f7f8f9;
    --tocsidebar-shadow: rgba(0,0,0,.1);
    --tocsidebar-heading-text: hsla(203,20%,40%,.7);

    --toclink-text: var(--text);
    --toclink-underline: #3980b5;
    --toclink-visited-text: var(--toclink-text);
    --toclink-visited-underline: #054572;

    --heading-text: #005a9c;

    --hr-text: var(--text);

    --algo-border: #def;

    --del-text: red;
    --del-bg: transparent;
    --ins-text: #080;
    --ins-bg: transparent;

    --a-normal-text: #034575;
    --a-normal-underline: #bbb;
    --a-visited-text: var(--a-normal-text);
    --a-visited-underline: #707070;
    --a-hover-bg: rgba(75%, 75%, 75%, .25);
    --a-active-text: #c00;
    --a-active-underline: #c00;

    --blockquote-border: silver;
    --blockquote-bg: transparent;
    --blockquote-text: currentcolor;

    --issue-border: #e05252;
    --issue-bg: #fbe9e9;
    --issue-text: var(--text);
    --issueheading-text: #831616;

    --example-border: #e0cb52;
    --example-bg: #fcfaee;
    --example-text: var(--text);
    --exampleheading-text: #574b0f;

    --note-border: #52e052;
    --note-bg: #e9fbe9;
    --note-text: var(--text);
    --noteheading-text: hsl(120, 70%, 30%);
    --notesummary-underline: silver;

    --assertion-border: #aaa;
    --assertion-bg: #eee;
    --assertion-text: black;

    --advisement-border: orange;
    --advisement-bg: #fec;
    --advisement-text: var(--text);
    --advisementheading-text: #b35f00;

    --warning-border: red;
    --warning-bg: hsla(40,100%,50%,0.95);
    --warning-text: var(--text);

    --amendment-border: #330099;
    --amendment-bg: #F5F0FF;
    --amendment-text: var(--text);
    --amendmentheading-text: #220066;

    --def-border: #8ccbf2;
    --def-bg: #def;
    --def-text: var(--text);
    --defrow-border: #bbd7e9;

    --datacell-border: silver;

    --indexinfo-text: #707070;

    --indextable-hover-text: black;
    --indextable-hover-bg: #f7f8f9;

    --outdatedspec-bg: rgba(0, 0, 0, .5);
    --outdatedspec-text: black;
    --outdated-bg: maroon;
    --outdated-text: white;
    --outdated-shadow: red;

    --editedrec-bg: darkorange;
}</style>
<style>/* style-counters */

body {
    counter-reset: example figure issue;
}
.issue {
    counter-increment: issue;
}
.issue:not(.no-marker)::before {
    content: "Issue " counter(issue);
}

.example {
    counter-increment: example;
}
.example:not(.no-marker)::before {
    content: "Example " counter(example);
}
.invalid.example:not(.no-marker)::before,
.illegal.example:not(.no-marker)::before {
    content: "Invalid Example" counter(example);
}

figcaption {
    counter-increment: figure;
}
figcaption:not(.no-marker)::before {
    content: "Figure " counter(figure) " ";
}</style>
<style>/* style-dfn-panel */

:root {
    --dfnpanel-bg: #ddd;
    --dfnpanel-text: var(--text);
}
.dfn-panel {
    position: absolute;
    z-index: 35;
    height: auto;
    width: -webkit-fit-content;
    width: fit-content;
    max-width: 300px;
    max-height: 500px;
    overflow: auto;
    padding: 0.5em 0.75em;
    font: small Helvetica Neue, sans-serif, Droid Sans Fallback;
    background: var(--dfnpanel-bg);
    color: var(--dfnpanel-text);
    border: outset 0.2em;
}
.dfn-panel:not(.on) { display: none; }
.dfn-panel * { margin: 0; padding: 0; text-indent: 0; }
.dfn-panel > b { display: block; }
.dfn-panel a { color: var(--dfnpanel-text); }
.dfn-panel a:not(:hover) { text-decoration: none !important; border-bottom: none !important; }
.dfn-panel > b + b { margin-top: 0.25em; }
.dfn-panel ul { padding: 0; }
.dfn-panel li { list-style: inside; }
.dfn-panel.activated {
    display: inline-block;
    position: fixed;
    left: .5em;
    bottom: 2em;
    margin: 0 auto;
    max-width: calc(100vw - 1.5em - .4em - .5em);
    max-height: 30vh;
}

.dfn-paneled { cursor: pointer; }
</style>
<style>/* style-issues */

a[href].issue-return {
    float: right;
    float: inline-end;
    color: var(--issueheading-text);
    font-weight: bold;
    text-decoration: none;
}
</style>
<style>/* style-md-lists */

/* This is a weird hack for me not yet following the commonmark spec
   regarding paragraph and lists. */
[data-md] > :first-child {
    margin-top: 0;
}
[data-md] > :last-child {
    margin-bottom: 0;
}</style>
<style>/* style-mdn-anno */

            @media (max-width: 767px) { .mdn-anno { opacity: .1 } }
            .mdn-anno { font: 1em sans-serif; padding: 0.3em; position: absolute; z-index: 8; right: 0.3em; background: #EEE; color: black; box-shadow: 0 0 3px #999; overflow: hidden; border-collapse: initial; border-spacing: initial; min-width: 9em; max-width: min-content; white-space: nowrap; word-wrap: normal; hyphens: none}
            .mdn-anno:not(.wrapped) { opacity: 1}
            .mdn-anno:hover { z-index: 9 }
            .mdn-anno.wrapped { min-width: 0 }
            .mdn-anno.wrapped > :not(button) { display: none; }
            .mdn-anno > .mdn-anno-btn { cursor: pointer; border: none; color: #000; background: transparent; margin: -8px; float: right; padding: 10px 8px 8px 8px; outline: none; }
            .mdn-anno > .mdn-anno-btn > .less-than-two-engines-flag { color: red; padding-right: 2px; }
            .mdn-anno > .mdn-anno-btn > .all-engines-flag { color: green; padding-right: 2px; }
            .mdn-anno > .mdn-anno-btn > span { color: #fff; background-color: #000; font-weight: normal; font-family: zillaslab, Palatino, "Palatino Linotype", serif; padding: 2px 3px 0px 3px; line-height: 1.3em; vertical-align: top; }
            .mdn-anno > .feature { margin-top: 20px; }
            .mdn-anno > .feature:not(:first-of-type) { border-top: 1px solid #999; margin-top: 6px; padding-top: 2px; }
            .mdn-anno > .feature > .less-than-two-engines-text { color: red }
            .mdn-anno > .feature > .all-engines-text { color: green }
            .mdn-anno > .feature > p { font-size: .75em; margin-top: 6px; margin-bottom: 0; }
            .mdn-anno > .feature > p + p { margin-top: 3px; }
            .mdn-anno > .feature > .support { display: block; font-size: 0.6em; margin: 0; padding: 0; margin-top: 2px }
            .mdn-anno > .feature > .support + div { padding-top: 0.5em; }
            .mdn-anno > .feature > .support > hr { display: block; border: none; border-top: 1px dotted #999; padding: 3px 0px 0px 0px; margin: 2px 3px 0px 3px; }
            .mdn-anno > .feature > .support > hr::before { content: ""; }
            .mdn-anno > .feature > .support > span { padding: 0.2em 0; display: block; display: table; }
            .mdn-anno > .feature > .support > span.no { color: #CCCCCC; filter: grayscale(100%); }
            .mdn-anno > .feature > .support > span.no::before { opacity: 0.5; }
            .mdn-anno > .feature > .support > span:first-of-type { padding-top: 0.5em; }
            .mdn-anno > .feature > .support > span > span { padding: 0 0.5em; display: table-cell; }
            .mdn-anno > .feature > .support > span > span:first-child { width: 100%; }
            .mdn-anno > .feature > .support > span > span:last-child { width: 100%; white-space: pre; padding: 0; }
            .mdn-anno > .feature > .support > span::before { content: ' '; display: table-cell; min-width: 1.5em; height: 1.5em; background: no-repeat center center; background-size: contain; text-align: right; font-size: 0.75em; font-weight: bold; }
            .mdn-anno > .feature > .support > .chrome_android::before { background-image: url(https://resources.whatwg.org/browser-logos/chrome.svg); }
            .mdn-anno > .feature > .support > .firefox_android::before { background-image: url(https://resources.whatwg.org/browser-logos/firefox.png); }
            .mdn-anno > .feature > .support > .chrome::before { background-image: url(https://resources.whatwg.org/browser-logos/chrome.svg); }
            .mdn-anno > .feature > .support > .edge_blink::before { background-image: url(https://resources.whatwg.org/browser-logos/edge.svg); }
            .mdn-anno > .feature > .support > .edge::before { background-image: url(https://resources.whatwg.org/browser-logos/edge_legacy.svg); }
            .mdn-anno > .feature > .support > .firefox::before { background-image: url(https://resources.whatwg.org/browser-logos/firefox.png); }
            .mdn-anno > .feature > .support > .ie::before { background-image: url(https://resources.whatwg.org/browser-logos/ie.png); }
            .mdn-anno > .feature > .support > .safari_ios::before { background-image: url(https://resources.whatwg.org/browser-logos/safari-ios.svg); }
            .mdn-anno > .feature > .support > .nodejs::before { background-image: url(https://nodejs.org/static/images/favicons/favicon.ico); }
            .mdn-anno > .feature > .support > .opera_android::before { background-image: url(https://resources.whatwg.org/browser-logos/opera.svg); }
            .mdn-anno > .feature > .support > .opera::before { background-image: url(https://resources.whatwg.org/browser-logos/opera.svg); }
            .mdn-anno > .feature > .support > .safari::before { background-image: url(https://resources.whatwg.org/browser-logos/safari.png); }
            .mdn-anno > .feature > .support > .samsunginternet_android::before { background-image: url(https://resources.whatwg.org/browser-logos/samsung.svg); }
            .mdn-anno > .feature > .support > .webview_android::before { background-image: url(https://resources.whatwg.org/browser-logos/android-webview.png); }
            .name-slug-mismatch { color: red }
            .caniuse-status:hover { z-index: 9; }

            /* dt, li, .issue, .note, and .example are "position: relative", so to put annotation at right margin, must move to right of containing block */
            .h-entry:not(.status-LS) dt > .mdn-anno, .h-entry:not(.status-LS) li > .mdn-anno, .h-entry:not(.status-LS) .issue > .mdn-anno, .h-entry:not(.status-LS) .note > .mdn-anno, .h-entry:not(.status-LS) .example > .mdn-anno { right: -6.7em; }
            .h-entry p + .mdn-anno { margin-top: 0; }
            h2 + .mdn-anno.after { margin: -48px 0 0 0; }
            h3 + .mdn-anno.after { margin: -46px 0 0 0; }
            h4 + .mdn-anno.after { margin: -42px 0 0 0; }
            h5 + .mdn-anno.after { margin: -40px 0 0 0; }
            h6 + .mdn-anno.after { margin: -40px 0 0 0; }
            </style>
<style>/* style-selflinks */

:root {
    --selflink-text: white;
    --selflink-bg: gray;
    --selflink-hover-text: black;
}
.heading, .issue, .note, .example, li, dt {
    position: relative;
}
a.self-link {
    position: absolute;
    top: 0;
    left: calc(-1 * (3.5rem - 26px));
    width: calc(3.5rem - 26px);
    height: 2em;
    text-align: center;
    border: none;
    transition: opacity .2s;
    opacity: .5;
}
a.self-link:hover {
    opacity: 1;
}
.heading > a.self-link {
    font-size: 83%;
}
li > a.self-link {
    left: calc(-1 * (3.5rem - 26px) - 2em);
}
dfn > a.self-link {
    top: auto;
    left: auto;
    opacity: 0;
    width: 1.5em;
    height: 1.5em;
    background: var(--selflink-bg);
    color: var(--selflink-text);
    font-style: normal;
    transition: opacity .2s, background-color .2s, color .2s;
}
dfn:hover > a.self-link {
    opacity: 1;
}
dfn > a.self-link:hover {
    color: var(--selflink-hover-text);
}

a.self-link::before            { content: "¶"; }
.heading > a.self-link::before { content: "§"; }
dfn > a.self-link::before      { content: "#"; }
</style>
<style>/* style-syntax-highlighting */

            pre.idl.highlight {
                background: var(--borderedblock-bg, var(--def-bg));
            }

code.highlight { padding: .1em; border-radius: .3em; }
pre.highlight, pre > code.highlight { display: block; padding: 1em; margin: .5em 0; overflow: auto; border-radius: 0; }

.highlight:not(.idl) { background: rgba(0, 0, 0, .03); }
c-[a] { color: #990055 } /* Keyword.Declaration */
c-[b] { color: #990055 } /* Keyword.Type */
c-[c] { color: #708090 } /* Comment */
c-[d] { color: #708090 } /* Comment.Multiline */
c-[e] { color: #0077aa } /* Name.Attribute */
c-[f] { color: #669900 } /* Name.Tag */
c-[g] { color: #222222 } /* Name.Variable */
c-[k] { color: #990055 } /* Keyword */
c-[l] { color: #000000 } /* Literal */
c-[m] { color: #000000 } /* Literal.Number */
c-[n] { color: #0077aa } /* Name */
c-[o] { color: #999999 } /* Operator */
c-[p] { color: #999999 } /* Punctuation */
c-[s] { color: #a67f59 } /* Literal.String */
c-[t] { color: #a67f59 } /* Literal.String.Single */
c-[u] { color: #a67f59 } /* Literal.String.Double */
c-[cp] { color: #708090 } /* Comment.Preproc */
c-[c1] { color: #708090 } /* Comment.Single */
c-[cs] { color: #708090 } /* Comment.Special */
c-[kc] { color: #990055 } /* Keyword.Constant */
c-[kn] { color: #990055 } /* Keyword.Namespace */
c-[kp] { color: #990055 } /* Keyword.Pseudo */
c-[kr] { color: #990055 } /* Keyword.Reserved */
c-[ld] { color: #000000 } /* Literal.Date */
c-[nc] { color: #0077aa } /* Name.Class */
c-[no] { color: #0077aa } /* Name.Constant */
c-[nd] { color: #0077aa } /* Name.Decorator */
c-[ni] { color: #0077aa } /* Name.Entity */
c-[ne] { color: #0077aa } /* Name.Exception */
c-[nf] { color: #0077aa } /* Name.Function */
c-[nl] { color: #0077aa } /* Name.Label */
c-[nn] { color: #0077aa } /* Name.Namespace */
c-[py] { color: #0077aa } /* Name.Property */
c-[ow] { color: #999999 } /* Operator.Word */
c-[mb] { color: #000000 } /* Literal.Number.Bin */
c-[mf] { color: #000000 } /* Literal.Number.Float */
c-[mh] { color: #000000 } /* Literal.Number.Hex */
c-[mi] { color: #000000 } /* Literal.Number.Integer */
c-[mo] { color: #000000 } /* Literal.Number.Oct */
c-[sb] { color: #a67f59 } /* Literal.String.Backtick */
c-[sc] { color: #a67f59 } /* Literal.String.Char */
c-[sd] { color: #a67f59 } /* Literal.String.Doc */
c-[se] { color: #a67f59 } /* Literal.String.Escape */
c-[sh] { color: #a67f59 } /* Literal.String.Heredoc */
c-[si] { color: #a67f59 } /* Literal.String.Interpol */
c-[sx] { color: #a67f59 } /* Literal.String.Other */
c-[sr] { color: #a67f59 } /* Literal.String.Regex */
c-[ss] { color: #a67f59 } /* Literal.String.Symbol */
c-[vc] { color: #0077aa } /* Name.Variable.Class */
c-[vg] { color: #0077aa } /* Name.Variable.Global */
c-[vi] { color: #0077aa } /* Name.Variable.Instance */
c-[il] { color: #000000 } /* Literal.Number.Integer.Long */
</style>
<style>/* style-darkmode */

@media (prefers-color-scheme: dark) {
    :root {
        --text: #ddd;
        --bg: black;

        --unofficial-watermark: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='400' height='400'%3E%3Cg fill='%23100808' transform='translate(200 200) rotate(-45) translate(-200 -200)' stroke='%23100808' stroke-width='3'%3E%3Ctext x='50%25' y='220' style='font: bold 70px sans-serif; text-anchor: middle; letter-spacing: 6px;'%3EUNOFFICIAL%3C/text%3E%3Ctext x='50%25' y='305' style='font: bold 70px sans-serif; text-anchor: middle; letter-spacing: 6px;'%3EDRAFT%3C/text%3E%3C/g%3E%3C/svg%3E");

        --logo-bg: #1a5e9a;
        --logo-active-bg: #c00;
        --logo-text: white;

        --tocnav-normal-text: #999;
        --tocnav-normal-bg: var(--bg);
        --tocnav-hover-text: var(--tocnav-normal-text);
        --tocnav-hover-bg: #080808;
        --tocnav-active-text: #f44;
        --tocnav-active-bg: var(--tocnav-normal-bg);

        --tocsidebar-text: var(--text);
        --tocsidebar-bg: #080808;
        --tocsidebar-shadow: rgba(255,255,255,.1);
        --tocsidebar-heading-text: hsla(203,20%,40%,.7);

        --toclink-text: var(--text);
        --toclink-underline: #6af;
        --toclink-visited-text: var(--toclink-text);
        --toclink-visited-underline: #054572;

        --heading-text: #8af;

        --hr-text: var(--text);

        --algo-border: #456;

        --del-text: #f44;
        --del-bg: transparent;
        --ins-text: #4a4;
        --ins-bg: transparent;

        --a-normal-text: #6af;
        --a-normal-underline: #555;
        --a-visited-text: var(--a-normal-text);
        --a-visited-underline: var(--a-normal-underline);
        --a-hover-bg: rgba(25%, 25%, 25%, .2);
        --a-active-text: #f44;
        --a-active-underline: var(--a-active-text);

        --borderedblock-bg: rgba(255, 255, 255, .05);

        --blockquote-border: silver;
        --blockquote-bg: var(--borderedblock-bg);
        --blockquote-text: currentcolor;

        --issue-border: #e05252;
        --issue-bg: var(--borderedblock-bg);
        --issue-text: var(--text);
        --issueheading-text: hsl(0deg, 70%, 70%);

        --example-border: hsl(50deg, 90%, 60%);
        --example-bg: var(--borderedblock-bg);
        --example-text: var(--text);
        --exampleheading-text: hsl(50deg, 70%, 70%);

        --note-border: hsl(120deg, 100%, 35%);
        --note-bg: var(--borderedblock-bg);
        --note-text: var(--text);
        --noteheading-text: hsl(120, 70%, 70%);
        --notesummary-underline: silver;

        --assertion-border: #444;
        --assertion-bg: var(--borderedblock-bg);
        --assertion-text: var(--text);

        --advisement-border: orange;
        --advisement-bg: #222218;
        --advisement-text: var(--text);
        --advisementheading-text: #f84;

        --warning-border: red;
        --warning-bg: hsla(40,100%,20%,0.95);
        --warning-text: var(--text);

        --amendment-border: #330099;
        --amendment-bg: #080010;
        --amendment-text: var(--text);
        --amendmentheading-text: #cc00ff;

        --def-border: #8ccbf2;
        --def-bg: #080818;
        --def-text: var(--text);
        --defrow-border: #136;

        --datacell-border: silver;

        --indexinfo-text: #aaa;

        --indextable-hover-text: var(--text);
        --indextable-hover-bg: #181818;

        --outdatedspec-bg: rgba(255, 255, 255, .5);
        --outdatedspec-text: black;
        --outdated-bg: maroon;
        --outdated-text: white;
        --outdated-shadow: red;

        --editedrec-bg: darkorange;
    }
    /* In case a transparent-bg image doesn't expect to be on a dark bg,
       which is quite common in practice... */
    img { background: white; }
}
@media (prefers-color-scheme: dark) {
    :root {
        --selflink-text: black;
        --selflink-bg: silver;
        --selflink-hover-text: white;
    }
}

@media (prefers-color-scheme: dark) {
    :root {
        --dfnpanel-bg: #222;
        --dfnpanel-text: var(--text);
    }
}
@media (prefers-color-scheme: dark) {
    .highlight:not(.idl) { background: rgba(255, 255, 255, .05); }

    c-[a] { color: #d33682 } /* Keyword.Declaration */
    c-[b] { color: #d33682 } /* Keyword.Type */
    c-[c] { color: #2aa198 } /* Comment */
    c-[d] { color: #2aa198 } /* Comment.Multiline */
    c-[e] { color: #268bd2 } /* Name.Attribute */
    c-[f] { color: #b58900 } /* Name.Tag */
    c-[g] { color: #cb4b16 } /* Name.Variable */
    c-[k] { color: #d33682 } /* Keyword */
    c-[l] { color: #657b83 } /* Literal */
    c-[m] { color: #657b83 } /* Literal.Number */
    c-[n] { color: #268bd2 } /* Name */
    c-[o] { color: #657b83 } /* Operator */
    c-[p] { color: #657b83 } /* Punctuation */
    c-[s] { color: #6c71c4 } /* Literal.String */
    c-[t] { color: #6c71c4 } /* Literal.String.Single */
    c-[u] { color: #6c71c4 } /* Literal.String.Double */
    c-[ch] { color: #2aa198 } /* Comment.Hashbang */
    c-[cp] { color: #2aa198 } /* Comment.Preproc */
    c-[cpf] { color: #2aa198 } /* Comment.PreprocFile */
    c-[c1] { color: #2aa198 } /* Comment.Single */
    c-[cs] { color: #2aa198 } /* Comment.Special */
    c-[kc] { color: #d33682 } /* Keyword.Constant */
    c-[kn] { color: #d33682 } /* Keyword.Namespace */
    c-[kp] { color: #d33682 } /* Keyword.Pseudo */
    c-[kr] { color: #d33682 } /* Keyword.Reserved */
    c-[ld] { color: #657b83 } /* Literal.Date */
    c-[nc] { color: #268bd2 } /* Name.Class */
    c-[no] { color: #268bd2 } /* Name.Constant */
    c-[nd] { color: #268bd2 } /* Name.Decorator */
    c-[ni] { color: #268bd2 } /* Name.Entity */
    c-[ne] { color: #268bd2 } /* Name.Exception */
    c-[nf] { color: #268bd2 } /* Name.Function */
    c-[nl] { color: #268bd2 } /* Name.Label */
    c-[nn] { color: #268bd2 } /* Name.Namespace */
    c-[py] { color: #268bd2 } /* Name.Property */
    c-[ow] { color: #657b83 } /* Operator.Word */
    c-[mb] { color: #657b83 } /* Literal.Number.Bin */
    c-[mf] { color: #657b83 } /* Literal.Number.Float */
    c-[mh] { color: #657b83 } /* Literal.Number.Hex */
    c-[mi] { color: #657b83 } /* Literal.Number.Integer */
    c-[mo] { color: #657b83 } /* Literal.Number.Oct */
    c-[sa] { color: #6c71c4 } /* Literal.String.Affix */
    c-[sb] { color: #6c71c4 } /* Literal.String.Backtick */
    c-[sc] { color: #6c71c4 } /* Literal.String.Char */
    c-[dl] { color: #6c71c4 } /* Literal.String.Delimiter */
    c-[sd] { color: #6c71c4 } /* Literal.String.Doc */
    c-[se] { color: #6c71c4 } /* Literal.String.Escape */
    c-[sh] { color: #6c71c4 } /* Literal.String.Heredoc */
    c-[si] { color: #6c71c4 } /* Literal.String.Interpol */
    c-[sx] { color: #6c71c4 } /* Literal.String.Other */
    c-[sr] { color: #6c71c4 } /* Literal.String.Regex */
    c-[ss] { color: #6c71c4 } /* Literal.String.Symbol */
    c-[fm] { color: #268bd2 } /* Name.Function.Magic */
    c-[vc] { color: #cb4b16 } /* Name.Variable.Class */
    c-[vg] { color: #cb4b16 } /* Name.Variable.Global */
    c-[vi] { color: #cb4b16 } /* Name.Variable.Instance */
    c-[vm] { color: #cb4b16 } /* Name.Variable.Magic */
    c-[il] { color: #657b83 } /* Literal.Number.Integer.Long */
}
</style>
 <body class="h-entry">
  <div class="head">
   <p data-fill-with="logo"><a class="logo" href="https://www.w3.org/"> <img alt="W3C" height="48" src="https://www.w3.org/StyleSheets/TR/2021/logos/W3C" width="72"> </a> </p>
   <h1 class="p-name no-ref" id="title">Compression Streams</h1>
   <p id="w3c-state"><a href="https://www.w3.org/standards/types#CG-DRAFT">Draft Community Group Report</a>, <time class="dt-updated" datetime="2022-08-15">15 August 2022</time></p>
   <div data-fill-with="spec-metadata">
    <dl>
     <dt>This version:
     <dd><a class="u-url" href="https://wicg.github.io/compression/">https://wicg.github.io/compression/</a>
     <dt>Issue Tracking:
     <dd><a href="https://github.com/wicg/compression/issues/">GitHub</a>
     <dt class="editor">Editors:
     <dd class="editor p-author h-card vcard"><span class="p-name fn">Canon Mukai</span> (<span class="p-org org">Google</span>)
     <dd class="editor p-author h-card vcard"><span class="p-name fn">Adam Rice</span> (<span class="p-org org">Google</span>)
    </dl>
   </div>
   <div data-fill-with="warning"></div>
   <p class="copyright" data-fill-with="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2022 the Contributors to the Compression Streams Specification, published by the <a href="https://www.w3.org/community/wicg/">Web Platform Incubator Community Group</a> under the <a href="https://www.w3.org/community/about/agreements/cla/">W3C Community Contributor License Agreement (CLA)</a>.
A human-readable <a href="http://www.w3.org/community/about/agreements/cla-deed/">summary</a> is available. </p>
   <hr title="Separator for header">
  </div>
  <div class="p-summary" data-fill-with="abstract">
   <h2 class="no-num no-toc no-ref heading settled" id="abstract"><span class="content">Abstract</span></h2>
   <p>This document defines a set of JavaScript APIs to compress and decompress

  streams of binary data.</p>
  </div>
  <div data-fill-with="at-risk"></div>
  <h2 class="no-num no-toc no-ref heading settled" id="status"><span class="content">Status of this document</span></h2>
  <div data-fill-with="status">
   <p> This specification was published by the <a href="https://www.w3.org/community/wicg/">Web Platform Incubator Community Group</a>.
  It is not a W3C Standard nor is it on the W3C Standards Track.

  Please note that under the <a href="https://www.w3.org/community/about/agreements/cla/">W3C Community Contributor License Agreement (CLA)</a> there is a limited opt-out and other conditions apply.

  Learn more about <a href="http://www.w3.org/community/">W3C Community and Business Groups</a>. </p>
   <p></p>
  </div>
  <div data-fill-with="at-risk"></div>
  <nav data-fill-with="table-of-contents" id="toc">
   <h2 class="no-num no-toc no-ref" id="contents">Table of Contents</h2>
   <ol class="toc" role="directory">
    <li><a href="#introduction"><span class="secno">1</span> <span class="content">Introduction</span></a>
    <li><a href="#conformance"><span class="secno">2</span> <span class="content">Conformance</span></a>
    <li><a href="#terminology"><span class="secno">3</span> <span class="content">Terminology</span></a>
    <li><a href="#supported-formats"><span class="secno">4</span> <span class="content">Supported formats</span></a>
    <li><a href="#compression-stream"><span class="secno">5</span> <span class="content">Interface <code>CompressionStream</code></span></a>
    <li><a href="#decompression-stream"><span class="secno">6</span> <span class="content">Interface <code>DecompressionStream</code></span></a>
    <li><a href="#privacy-security"><span class="secno">7</span> <span class="content">Privacy and Security Considerations</span></a>
    <li>
     <a href="#examples"><span class="secno">8</span> <span class="content">Examples</span></a>
     <ol class="toc">
      <li><a href="#example-gzip-compress-stream"><span class="secno">8.1</span> <span class="content">Gzip-compress a stream</span></a>
      <li><a href="#example-deflate-compress"><span class="secno">8.2</span> <span class="content">Deflate-compress an ArrayBuffer to a Uint8Array</span></a>
      <li><a href="#example-gzip-decompress"><span class="secno">8.3</span> <span class="content">Gzip-decompress a Blob to Blob</span></a>
     </ol>
    <li><a href="#acknowledgments"><span class="secno">9</span> <span class="content">Acknowledgments</span></a>
    <li>
     <a href="#index"><span class="secno"></span> <span class="content">Index</span></a>
     <ol class="toc">
      <li><a href="#index-defined-here"><span class="secno"></span> <span class="content">Terms defined by this specification</span></a>
      <li><a href="#index-defined-elsewhere"><span class="secno"></span> <span class="content">Terms defined by reference</span></a>
     </ol>
    <li>
     <a href="#references"><span class="secno"></span> <span class="content">References</span></a>
     <ol class="toc">
      <li><a href="#normative"><span class="secno"></span> <span class="content">Normative References</span></a>
      <li><a href="#informative"><span class="secno"></span> <span class="content">Informative References</span></a>
     </ol>
    <li><a href="#idl-index"><span class="secno"></span> <span class="content">IDL Index</span></a>
   </ol>
  </nav>
  <main>
   <h2 class="heading settled" data-level="1" id="introduction"><span class="secno">1. </span><span class="content">Introduction</span><a class="self-link" href="#introduction"></a></h2>
   <p><em>This section is non-normative.</em></p>
   <p>The APIs specified in this specification are used to compress and decompress streams of data. They support "deflate", "deflate-raw" and "gzip" as compression algorithms. They are widely used by web developers.</p>
   <h2 class="heading settled" data-level="2" id="conformance"><span class="secno">2. </span><span class="content">Conformance</span><a class="self-link" href="#conformance"></a></h2>
   <p>As well as sections marked as non-normative, all authoring guidelines,
diagrams, examples, and notes in this specification are non-normative.
Everything else in this specification is normative.</p>
   <p>The key words <em>MUST</em> and <em>SHOULD</em> are to be interpreted as described in <a data-link-type="biblio" href="#biblio-rfc2119">[RFC2119]</a>.</p>
   <p>This specification defines conformance criteria that apply to a single product:
the user agent that implements the interfaces that it contains.</p>
   <p>Conformance requirements phrased as algorithms or specific steps may be
implemented in any manner, so long as the end result is equivalent. (In
particular, the algorithms defined in this specification are intended to be
easy to follow, and not intended to be performant.)</p>
   <p>Implementations that use ECMAScript to implement the APIs defined in this
specification MUST implement them in a manner consistent with the ECMAScript
Bindings defined in the Web IDL specification <a data-link-type="biblio" href="#biblio-webidl">[WebIDL]</a>, as this
specification uses that specification and terminology.</p>
   <h2 class="heading settled" data-level="3" id="terminology"><span class="secno">3. </span><span class="content">Terminology</span><a class="self-link" href="#terminology"></a></h2>
   <p>A chunk is a piece of data. In the case of CompressionStream and DecompressionStream, the output chunk type is Uint8Array. They accept any <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#BufferSource" id="ref-for-BufferSource">BufferSource</a></code> type as input.</p>
   <p>A stream represents an ordered sequence of chunks. The terms <code class="idl"><a data-link-type="idl" href="https://streams.spec.whatwg.org/#readablestream" id="ref-for-readablestream">ReadableStream</a></code> and <code class="idl"><a data-link-type="idl" href="https://streams.spec.whatwg.org/#writablestream" id="ref-for-writablestream">WritableStream</a></code> are defined in <a data-link-type="biblio" href="#biblio-whatwg-streams">[WHATWG-STREAMS]</a>.</p>
   <p>A <dfn class="dfn-paneled" data-dfn-type="dfn" data-noexport id="compression-context">compression context</dfn> is the internal state maintained by a compression or decompression algorithm. The contents of a <a data-link-type="dfn" href="#compression-context" id="ref-for-compression-context">compression context</a> depend on the format, algorithm and implementation in use. From the point of view of this specification, it is an opaque object. A <a data-link-type="dfn" href="#compression-context" id="ref-for-compression-context①">compression context</a> is initially in a start state such that it anticipates the first byte of input.</p>
   <h2 class="heading settled" data-level="4" id="supported-formats"><span class="secno">4. </span><span class="content">Supported formats</span><a class="self-link" href="#supported-formats"></a></h2>
   <dl>
    <dt data-md><code>deflate</code>
    <dd data-md>
     <p>"ZLIB Compressed Data Format" <a data-link-type="biblio" href="#biblio-rfc1950">[RFC1950]</a></p>
     <p class="note" role="note"><span>Note:</span> This format is referred to as "deflate" for consistency with HTTP Content-Encodings. See <a data-biblio-obsolete data-link-type="biblio" href="#biblio-rfc7230">[RFC7230]</a> section 4.2.2.</p>
     <ul>
      <li data-md>
       <p>Implementations must be "compliant" as described in <a data-link-type="biblio" href="#biblio-rfc1950">[RFC1950]</a> section 2.3.</p>
      <li data-md>
       <p>Field values described as invalid in <a data-link-type="biblio" href="#biblio-rfc1950">[RFC1950]</a> must not be created by CompressionStream, and are errors for DecompressionStream.</p>
      <li data-md>
       <p>The only valid value of the <code>CM</code> (Compression method) part of the <code>CMF</code> field is 8.</p>
      <li data-md>
       <p>The <code>FDICT</code> flag is not supported by these APIs, and will error the stream if set.</p>
      <li data-md>
       <p>The <code>FLEVEL</code> flag is ignored by DecompressionStream.</p>
      <li data-md>
       <p>It is an error for DecompressionStream if the <code>ADLER32</code> checksum is not correct.</p>
      <li data-md>
       <p>It is an error if there is additional input data after the <code>ADLER32</code> checksum.</p>
     </ul>
    <dt data-md><code>deflate-raw</code>
    <dd data-md>
     <p>"The DEFLATE algorithm" <a data-link-type="biblio" href="#biblio-rfc1951">[RFC1951]</a></p>
     <ul>
      <li data-md>
       <p>Implementations must be "compliant" as described in <a data-link-type="biblio" href="#biblio-rfc1951">[RFC1951]</a> section 1.4.</p>
      <li data-md>
       <p>Non-<a data-link-type="biblio" href="#biblio-rfc1951">[RFC1951]</a>-conforming blocks must not be created by CompressionStream, and are errors for DecompressionStream.</p>
     </ul>
    <dt data-md><code>gzip</code>
    <dd data-md>
     <p>"GZIP file format" <a data-link-type="biblio" href="#biblio-rfc1952">[RFC1952]</a></p>
     <ul>
      <li data-md>
       <p>Implementations must be "compliant" as described in <a data-link-type="biblio" href="#biblio-rfc1952">[RFC1952]</a> section 2.3.1.2.</p>
      <li data-md>
       <p>Field values described as invalid in <a data-link-type="biblio" href="#biblio-rfc1952">[RFC1952]</a> must not be created by CompressionStream, and are errors for DecompressionStream.</p>
      <li data-md>
       <p>The only valid value of the <code>CM</code> (Compression Method) field is 8.</p>
      <li data-md>
       <p>The <code>FTEXT</code> flag must be ignored by DecompressionStream.</p>
      <li data-md>
       <p>If the <code>FHCRC</code> field is present, it is an error for it to be incorrect.</p>
      <li data-md>
       <p>The contents of any <code>FEXTRA</code>, <code>FNAME</code> and <code>FCOMMENT</code> fields must be ignored by DecompressionStream, except to verify that they are terminated correctly.</p>
      <li data-md>
       <p>The contents of the <code>MTIME</code>, <code>XFL</code> and <code>OS</code> fields must be ignored by DecompressionStream.</p>
      <li data-md>
       <p>It is an error if <code>CRC32</code> or <code>ISIZE</code> do not match the decompressed data.</p>
      <li data-md>
       <p>A <code>gzip</code> stream may only contain one "member".</p>
      <li data-md>
       <p>It is an error if there is additional input data after the end of the "member".</p>
     </ul>
   </dl>
   <h2 class="heading settled" data-level="5" id="compression-stream"><span class="secno">5. </span><span class="content">Interface <code>CompressionStream</code></span><a class="self-link" href="#compression-stream"></a></h2>
   <div class="mdn-anno wrapped after">
    <button class="mdn-anno-btn"><b class="less-than-two-engines-flag" title="This feature is in less than two current engines.">⚠</b><span>MDN</span></button>
    <div class="feature">
     <p><a href="https://developer.mozilla.org/en-US/docs/Web/API/CompressionStream" title="The CompressionStream interface of the Compression Streams API is an API for compressing a stream of data.">CompressionStream</a></p>
     <p class="less-than-two-engines-text">In only one current engine.</p>
     <div class="support">
      <span class="firefox no"><span>Firefox</span><span>None</span></span><span class="safari no"><span>Safari</span><span>None</span></span><span class="chrome yes"><span>Chrome</span><span>80+</span></span>
      <hr>
      <span class="opera no"><span>Opera</span><span>?</span></span><span class="edge_blink yes"><span>Edge</span><span>80+</span></span>
      <hr>
      <span class="edge no"><span>Edge (Legacy)</span><span>?</span></span><span class="ie no"><span>IE</span><span>None</span></span>
      <hr>
      <span class="firefox_android no"><span>Firefox for Android</span><span>?</span></span><span class="safari_ios no"><span>iOS Safari</span><span>?</span></span><span class="chrome_android no"><span>Chrome for Android</span><span>?</span></span><span class="webview_android no"><span>Android WebView</span><span>?</span></span><span class="samsunginternet_android no"><span>Samsung Internet</span><span>?</span></span><span class="opera_android no"><span>Opera Mobile</span><span>?</span></span>
     </div>
    </div>
   </div>
<pre class="idl highlight def">[Exposed=*]
<c- b>interface</c-> <dfn class="dfn-paneled idl-code" data-dfn-type="interface" data-export id="compressionstream"><code><c- g>CompressionStream</c-></code></dfn> {
  <a class="idl-code" data-link-type="constructor" href="#dom-compressionstream-compressionstream" id="ref-for-dom-compressionstream-compressionstream"><c- g>constructor</c-></a>(<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString" id="ref-for-idl-DOMString"><c- b>DOMString</c-></a> <dfn class="idl-code" data-dfn-for="CompressionStream/CompressionStream(format), CompressionStream/constructor(format)" data-dfn-type="argument" data-export id="dom-compressionstream-compressionstream-format-format"><code><c- g>format</c-></code><a class="self-link" href="#dom-compressionstream-compressionstream-format-format"></a></dfn>);
};
<a data-link-type="idl-name" href="#compressionstream" id="ref-for-compressionstream"><c- n>CompressionStream</c-></a> <c- b>includes</c-> <a data-link-type="idl-name" href="https://streams.spec.whatwg.org/#generictransformstream" id="ref-for-generictransformstream"><c- n>GenericTransformStream</c-></a>;
</pre>
   <p>A <code class="idl"><a data-link-type="idl" href="#compressionstream" id="ref-for-compressionstream①">CompressionStream</a></code> has an associated <dfn class="dfn-paneled" data-dfn-for="CompressionStream" data-dfn-type="dfn" data-noexport id="compressionstream-format">format</dfn> and <a data-link-type="dfn" href="#compression-context" id="ref-for-compression-context②">compression context</a> <dfn class="dfn-paneled" data-dfn-for="CompressionStream" data-dfn-type="dfn" data-noexport id="compressionstream-context">context</dfn>.</p>
   <div class="mdn-anno wrapped">
    <button class="mdn-anno-btn"><b class="less-than-two-engines-flag" title="This feature is in less than two current engines.">⚠</b><span>MDN</span></button>
    <div class="feature">
     <p><a href="https://developer.mozilla.org/en-US/docs/Web/API/CompressionStream/CompressionStream" title="The CompressionStream() constructor creates a new CompressionStream object which compresses a stream of data.">CompressionStream/CompressionStream</a></p>
     <p class="less-than-two-engines-text">In only one current engine.</p>
     <div class="support">
      <span class="firefox no"><span>Firefox</span><span>None</span></span><span class="safari no"><span>Safari</span><span>None</span></span><span class="chrome yes"><span>Chrome</span><span>80+</span></span>
      <hr>
      <span class="opera no"><span>Opera</span><span>?</span></span><span class="edge_blink yes"><span>Edge</span><span>80+</span></span>
      <hr>
      <span class="edge no"><span>Edge (Legacy)</span><span>?</span></span><span class="ie no"><span>IE</span><span>None</span></span>
      <hr>
      <span class="firefox_android no"><span>Firefox for Android</span><span>?</span></span><span class="safari_ios no"><span>iOS Safari</span><span>?</span></span><span class="chrome_android no"><span>Chrome for Android</span><span>?</span></span><span class="webview_android no"><span>Android WebView</span><span>?</span></span><span class="samsunginternet_android no"><span>Samsung Internet</span><span>?</span></span><span class="opera_android no"><span>Opera Mobile</span><span>?</span></span>
      <hr>
      <span class="nodejs yes"><span>Node.js</span><span>17.0.0+</span></span>
     </div>
    </div>
   </div>
   <p>The <dfn class="dfn-paneled idl-code" data-dfn-for="CompressionStream" data-dfn-type="constructor" data-export data-lt="CompressionStream(format)|constructor(format)" id="dom-compressionstream-compressionstream"><code>new CompressionStream(<var>format</var>)</code></dfn> steps are:</p>
   <ol>
    <li data-md>
     <p>If <em>format</em> is unsupported in <code class="idl"><a data-link-type="idl" href="#compressionstream" id="ref-for-compressionstream②">CompressionStream</a></code>, then throw a <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#exceptiondef-typeerror" id="ref-for-exceptiondef-typeerror">TypeError</a></code>.</p>
    <li data-md>
     <p>Set <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#this" id="ref-for-this">this</a>'s <a data-link-type="dfn" href="#compressionstream-format" id="ref-for-compressionstream-format">format</a> to <em>format</em>.</p>
    <li data-md>
     <p>Let <em>transformAlgorithm</em> be an algorithm which takes a <em>chunk</em> argument and runs the <a data-link-type="dfn" href="#compress-and-enqueue-a-chunk" id="ref-for-compress-and-enqueue-a-chunk">compress and enqueue a chunk</a> algorithm with <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#this" id="ref-for-this①">this</a> and <em>chunk</em>.</p>
    <li data-md>
     <p>Let <em>flushAlgorithm</em> be an algorithm which takes no argument and runs the <a data-link-type="dfn" href="#compress-flush-and-enqueue" id="ref-for-compress-flush-and-enqueue">compress flush and enqueue</a> algorithm with <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#this" id="ref-for-this②">this</a>.</p>
    <li data-md>
     <p>Set <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#this" id="ref-for-this③">this</a>'s <a data-link-type="dfn" href="https://streams.spec.whatwg.org/#generictransformstream-transform" id="ref-for-generictransformstream-transform">transform</a> to a <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#new" id="ref-for-new">new</a> <code class="idl"><a data-link-type="idl" href="https://streams.spec.whatwg.org/#transformstream" id="ref-for-transformstream">TransformStream</a></code>.</p>
    <li data-md>
     <p><a data-link-type="dfn" href="https://streams.spec.whatwg.org/#transformstream-set-up" id="ref-for-transformstream-set-up">Set up</a> <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#this" id="ref-for-this④">this</a>'s <a data-link-type="dfn" href="https://streams.spec.whatwg.org/#generictransformstream-transform" id="ref-for-generictransformstream-transform①">transform</a> with <i><a data-link-type="dfn" href="https://streams.spec.whatwg.org/#transformstream-set-up-transformalgorithm" id="ref-for-transformstream-set-up-transformalgorithm">transformAlgorithm</a></i> set to <em>transformAlgorithm</em> and <i><a data-link-type="dfn" href="https://streams.spec.whatwg.org/#transformstream-set-up-flushalgorithm" id="ref-for-transformstream-set-up-flushalgorithm">flushAlgorithm</a></i> set to <em>flushAlgorithm</em>.</p>
   </ol>
   <p>The <dfn class="dfn-paneled" data-dfn-type="dfn" data-noexport id="compress-and-enqueue-a-chunk">compress and enqueue a chunk</dfn> algorithm, given a <code class="idl"><a data-link-type="idl" href="#compressionstream" id="ref-for-compressionstream③">CompressionStream</a></code> object <em>cs</em> and a <em>chunk</em>, runs these steps:</p>
   <ol>
    <li data-md>
     <p>If <em>chunk</em> is not a <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#BufferSource" id="ref-for-BufferSource①">BufferSource</a></code> type, then throw a <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#exceptiondef-typeerror" id="ref-for-exceptiondef-typeerror①">TypeError</a></code>.</p>
    <li data-md>
     <p>Let <em>buffer</em> be the result of compressing <em>chunk</em> with <em>cs</em>'s <a data-link-type="dfn" href="#compressionstream-format" id="ref-for-compressionstream-format①">format</a> and <a data-link-type="dfn" href="#compressionstream-context" id="ref-for-compressionstream-context">context</a>.</p>
    <li data-md>
     <p>If <em>buffer</em> is empty, return.</p>
    <li data-md>
     <p>Split <em>buffer</em> into one or more non-empty pieces and convert them into <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-Uint8Array" id="ref-for-idl-Uint8Array">Uint8Array</a></code>s.</p>
    <li data-md>
     <p>For each <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-Uint8Array" id="ref-for-idl-Uint8Array①">Uint8Array</a></code> <em>array</em>, <a data-link-type="dfn" href="https://streams.spec.whatwg.org/#transformstream-enqueue" id="ref-for-transformstream-enqueue">enqueue</a> <em>array</em> in <em>cs</em>'s <a data-link-type="dfn" href="https://streams.spec.whatwg.org/#generictransformstream-transform" id="ref-for-generictransformstream-transform②">transform</a>.</p>
   </ol>
   <p>The <dfn class="dfn-paneled" data-dfn-type="dfn" data-noexport id="compress-flush-and-enqueue">compress flush and enqueue</dfn> algorithm, which handles the end of data from the input <code class="idl"><a data-link-type="idl" href="https://streams.spec.whatwg.org/#readablestream" id="ref-for-readablestream①">ReadableStream</a></code> object, given a <code class="idl"><a data-link-type="idl" href="#compressionstream" id="ref-for-compressionstream④">CompressionStream</a></code> object <em>cs</em>, runs these steps:</p>
   <ol>
    <li data-md>
     <p>Let <em>buffer</em> be the result of compressing an empty input with <em>cs</em>'s <a data-link-type="dfn" href="#compressionstream-format" id="ref-for-compressionstream-format②">format</a> and <a data-link-type="dfn" href="#compressionstream-context" id="ref-for-compressionstream-context①">context</a>, with the finish flag.</p>
    <li data-md>
     <p>If <em>buffer</em> is empty, return.</p>
    <li data-md>
     <p>Split <em>buffer</em> into one or more non-empty pieces and convert them into <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-Uint8Array" id="ref-for-idl-Uint8Array②">Uint8Array</a></code>s.</p>
    <li data-md>
     <p>For each <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-Uint8Array" id="ref-for-idl-Uint8Array③">Uint8Array</a></code> <em>array</em>, <a data-link-type="dfn" href="https://streams.spec.whatwg.org/#transformstream-enqueue" id="ref-for-transformstream-enqueue①">enqueue</a> <em>array</em> in <em>cs</em>'s <a data-link-type="dfn" href="https://streams.spec.whatwg.org/#generictransformstream-transform" id="ref-for-generictransformstream-transform③">transform</a>.</p>
   </ol>
   <h2 class="heading settled" data-level="6" id="decompression-stream"><span class="secno">6. </span><span class="content">Interface <code>DecompressionStream</code></span><a class="self-link" href="#decompression-stream"></a></h2>
   <div class="mdn-anno wrapped after">
    <button class="mdn-anno-btn"><b class="less-than-two-engines-flag" title="This feature is in less than two current engines.">⚠</b><span>MDN</span></button>
    <div class="feature">
     <p><a href="https://developer.mozilla.org/en-US/docs/Web/API/DecompressionStream" title="The DecompressionStream interface of the Compression Streams API is an API for decompressing a stream of data.">DecompressionStream</a></p>
     <p class="less-than-two-engines-text">In only one current engine.</p>
     <div class="support">
      <span class="firefox no"><span>Firefox</span><span>None</span></span><span class="safari no"><span>Safari</span><span>None</span></span><span class="chrome yes"><span>Chrome</span><span>80+</span></span>
      <hr>
      <span class="opera no"><span>Opera</span><span>?</span></span><span class="edge_blink yes"><span>Edge</span><span>80+</span></span>
      <hr>
      <span class="edge no"><span>Edge (Legacy)</span><span>?</span></span><span class="ie no"><span>IE</span><span>None</span></span>
      <hr>
      <span class="firefox_android no"><span>Firefox for Android</span><span>?</span></span><span class="safari_ios no"><span>iOS Safari</span><span>?</span></span><span class="chrome_android no"><span>Chrome for Android</span><span>?</span></span><span class="webview_android no"><span>Android WebView</span><span>?</span></span><span class="samsunginternet_android no"><span>Samsung Internet</span><span>?</span></span><span class="opera_android no"><span>Opera Mobile</span><span>?</span></span>
     </div>
    </div>
   </div>
<pre class="idl highlight def">[Exposed=*]
<c- b>interface</c-> <dfn class="dfn-paneled idl-code" data-dfn-type="interface" data-export id="decompressionstream"><code><c- g>DecompressionStream</c-></code></dfn> {
  <a class="idl-code" data-link-type="constructor" href="#dom-decompressionstream-decompressionstream" id="ref-for-dom-decompressionstream-decompressionstream"><c- g>constructor</c-></a>(<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString" id="ref-for-idl-DOMString①"><c- b>DOMString</c-></a> <dfn class="idl-code" data-dfn-for="DecompressionStream/DecompressionStream(format), DecompressionStream/constructor(format)" data-dfn-type="argument" data-export id="dom-decompressionstream-decompressionstream-format-format"><code><c- g>format</c-></code><a class="self-link" href="#dom-decompressionstream-decompressionstream-format-format"></a></dfn>);
};
<a data-link-type="idl-name" href="#decompressionstream" id="ref-for-decompressionstream"><c- n>DecompressionStream</c-></a> <c- b>includes</c-> <a data-link-type="idl-name" href="https://streams.spec.whatwg.org/#generictransformstream" id="ref-for-generictransformstream①"><c- n>GenericTransformStream</c-></a>;
</pre>
   <p>A <code class="idl"><a data-link-type="idl" href="#decompressionstream" id="ref-for-decompressionstream①">DecompressionStream</a></code> has an associated <dfn class="dfn-paneled" data-dfn-for="DecompressionStream" data-dfn-type="dfn" data-noexport id="decompressionstream-format">format</dfn> and <a data-link-type="dfn" href="#compression-context" id="ref-for-compression-context③">compression context</a> <dfn class="dfn-paneled" data-dfn-for="DecompressionStream" data-dfn-type="dfn" data-noexport id="decompressionstream-context">context</dfn>.</p>
   <div class="mdn-anno wrapped">
    <button class="mdn-anno-btn"><b class="less-than-two-engines-flag" title="This feature is in less than two current engines.">⚠</b><span>MDN</span></button>
    <div class="feature">
     <p><a href="https://developer.mozilla.org/en-US/docs/Web/API/DecompressionStream/DecompressionStream" title="The DecompressionStream() constructor creates a new DecompressionStream object which decompresses a stream of data.">DecompressionStream/DecompressionStream</a></p>
     <p class="less-than-two-engines-text">In only one current engine.</p>
     <div class="support">
      <span class="firefox no"><span>Firefox</span><span>None</span></span><span class="safari no"><span>Safari</span><span>None</span></span><span class="chrome yes"><span>Chrome</span><span>80+</span></span>
      <hr>
      <span class="opera no"><span>Opera</span><span>?</span></span><span class="edge_blink yes"><span>Edge</span><span>80+</span></span>
      <hr>
      <span class="edge no"><span>Edge (Legacy)</span><span>?</span></span><span class="ie no"><span>IE</span><span>None</span></span>
      <hr>
      <span class="firefox_android no"><span>Firefox for Android</span><span>?</span></span><span class="safari_ios no"><span>iOS Safari</span><span>?</span></span><span class="chrome_android no"><span>Chrome for Android</span><span>?</span></span><span class="webview_android no"><span>Android WebView</span><span>?</span></span><span class="samsunginternet_android no"><span>Samsung Internet</span><span>?</span></span><span class="opera_android no"><span>Opera Mobile</span><span>?</span></span>
      <hr>
      <span class="nodejs yes"><span>Node.js</span><span>17.0.0+</span></span>
     </div>
    </div>
   </div>
   <p>The <dfn class="dfn-paneled idl-code" data-dfn-for="DecompressionStream" data-dfn-type="constructor" data-export data-lt="DecompressionStream(format)|constructor(format)" id="dom-decompressionstream-decompressionstream"><code>new DecompressionStream(<var>format</var>)</code></dfn> steps are:</p>
   <ol>
    <li data-md>
     <p>If <em>format</em> is unsupported in <code class="idl"><a data-link-type="idl" href="#decompressionstream" id="ref-for-decompressionstream②">DecompressionStream</a></code>, then throw a <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#exceptiondef-typeerror" id="ref-for-exceptiondef-typeerror②">TypeError</a></code>.</p>
    <li data-md>
     <p>Set <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#this" id="ref-for-this⑤">this</a>'s <a data-link-type="dfn" href="#decompressionstream-format" id="ref-for-decompressionstream-format">format</a> to <em>format</em>.</p>
    <li data-md>
     <p>Let <em>transformAlgorithm</em> be an algorithm which takes a <em>chunk</em> argument and runs the <a data-link-type="dfn" href="#decompress-and-enqueue-a-chunk" id="ref-for-decompress-and-enqueue-a-chunk">decompress and enqueue a chunk</a> algorithm with <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#this" id="ref-for-this⑥">this</a> and <em>chunk</em>.</p>
    <li data-md>
     <p>Let <em>flushAlgorithm</em> be an algorithm which takes no argument and runs the <a data-link-type="dfn" href="#decompress-flush-and-enqueue" id="ref-for-decompress-flush-and-enqueue">decompress flush and enqueue</a> algorithm with <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#this" id="ref-for-this⑦">this</a>.</p>
    <li data-md>
     <p>Set <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#this" id="ref-for-this⑧">this</a>'s <a data-link-type="dfn" href="https://streams.spec.whatwg.org/#generictransformstream-transform" id="ref-for-generictransformstream-transform④">transform</a> to a <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#new" id="ref-for-new①">new</a> <code class="idl"><a data-link-type="idl" href="https://streams.spec.whatwg.org/#transformstream" id="ref-for-transformstream①">TransformStream</a></code>.</p>
    <li data-md>
     <p><a data-link-type="dfn" href="https://streams.spec.whatwg.org/#transformstream-set-up" id="ref-for-transformstream-set-up①">Set up</a> <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#this" id="ref-for-this⑨">this</a>'s <a data-link-type="dfn" href="https://streams.spec.whatwg.org/#generictransformstream-transform" id="ref-for-generictransformstream-transform⑤">transform</a> with <i><a data-link-type="dfn" href="https://streams.spec.whatwg.org/#transformstream-set-up-transformalgorithm" id="ref-for-transformstream-set-up-transformalgorithm①">transformAlgorithm</a></i> set to <em>transformAlgorithm</em> and <i><a data-link-type="dfn" href="https://streams.spec.whatwg.org/#transformstream-set-up-flushalgorithm" id="ref-for-transformstream-set-up-flushalgorithm①">flushAlgorithm</a></i> set to <em>flushAlgorithm</em>.</p>
   </ol>
   <p>The <dfn class="dfn-paneled" data-dfn-type="dfn" data-noexport id="decompress-and-enqueue-a-chunk">decompress and enqueue a chunk</dfn> algorithm, given a <code class="idl"><a data-link-type="idl" href="#decompressionstream" id="ref-for-decompressionstream③">DecompressionStream</a></code> object <em>ds</em> and a <em>chunk</em>, runs these steps:</p>
   <ol>
    <li data-md>
     <p>If <em>chunk</em> is not a <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#BufferSource" id="ref-for-BufferSource②">BufferSource</a></code> type, then throw a <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#exceptiondef-typeerror" id="ref-for-exceptiondef-typeerror③">TypeError</a></code>.</p>
    <li data-md>
     <p>Let <em>buffer</em> be the result of decompressing <em>chunk</em> with <em>ds</em>'s <a data-link-type="dfn" href="#decompressionstream-format" id="ref-for-decompressionstream-format①">format</a> and <a data-link-type="dfn" href="#decompressionstream-context" id="ref-for-decompressionstream-context">context</a>. If this results in an error, then throw a <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#exceptiondef-typeerror" id="ref-for-exceptiondef-typeerror④">TypeError</a></code>.</p>
    <li data-md>
     <p>If <em>buffer</em> is empty, return.</p>
    <li data-md>
     <p>Split <em>buffer</em> into one or more non-empty pieces and convert them into <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-Uint8Array" id="ref-for-idl-Uint8Array④">Uint8Array</a></code>s.</p>
    <li data-md>
     <p>For each <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-Uint8Array" id="ref-for-idl-Uint8Array⑤">Uint8Array</a></code> <em>array</em>, <a data-link-type="dfn" href="https://streams.spec.whatwg.org/#transformstream-enqueue" id="ref-for-transformstream-enqueue②">enqueue</a> <em>array</em> in <em>ds</em>'s <a data-link-type="dfn" href="https://streams.spec.whatwg.org/#generictransformstream-transform" id="ref-for-generictransformstream-transform⑥">transform</a>.</p>
   </ol>
   <p>The <dfn class="dfn-paneled" data-dfn-type="dfn" data-noexport id="decompress-flush-and-enqueue">decompress flush and enqueue</dfn> algorithm, which handles the end of data from the input <code class="idl"><a data-link-type="idl" href="https://streams.spec.whatwg.org/#readablestream" id="ref-for-readablestream②">ReadableStream</a></code> object, given a <code class="idl"><a data-link-type="idl" href="#decompressionstream" id="ref-for-decompressionstream④">DecompressionStream</a></code> object <em>ds</em>, runs these steps:</p>
   <ol>
    <li data-md>
     <p>Let <em>buffer</em> be the result of decompressing an empty input with <em>ds</em>'s <a data-link-type="dfn" href="#decompressionstream-format" id="ref-for-decompressionstream-format②">format</a> and <a data-link-type="dfn" href="#decompressionstream-context" id="ref-for-decompressionstream-context①">context</a>, with the finish flag.</p>
    <li data-md>
     <p>If the end of the compressed input has not been reached, then throw a <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#exceptiondef-typeerror" id="ref-for-exceptiondef-typeerror⑤">TypeError</a></code>.</p>
    <li data-md>
     <p>If <em>buffer</em> is empty, return.</p>
    <li data-md>
     <p>Split <em>buffer</em> into one or more non-empty pieces and convert them into <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-Uint8Array" id="ref-for-idl-Uint8Array⑥">Uint8Array</a></code>s.</p>
    <li data-md>
     <p>For each <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-Uint8Array" id="ref-for-idl-Uint8Array⑦">Uint8Array</a></code> <em>array</em>, <a data-link-type="dfn" href="https://streams.spec.whatwg.org/#transformstream-enqueue" id="ref-for-transformstream-enqueue③">enqueue</a> <em>array</em> in <em>ds</em>'s <a data-link-type="dfn" href="https://streams.spec.whatwg.org/#generictransformstream-transform" id="ref-for-generictransformstream-transform⑦">transform</a>.</p>
   </ol>
   <h2 class="heading settled" data-level="7" id="privacy-security"><span class="secno">7. </span><span class="content">Privacy and Security Considerations</span><a class="self-link" href="#privacy-security"></a></h2>
   <p>The API doesn’t add any new privileges to the web platform.</p>
   <p>However, web developers have to pay attention to the situation when attackers can get the length of the data. If so, they may be able to guess the contents of the data.</p>
   <h2 class="heading settled" data-level="8" id="examples"><span class="secno">8. </span><span class="content">Examples</span><a class="self-link" href="#examples"></a></h2>
   <h3 class="heading settled" data-level="8.1" id="example-gzip-compress-stream"><span class="secno">8.1. </span><span class="content">Gzip-compress a stream</span><a class="self-link" href="#example-gzip-compress-stream"></a></h3>
<pre class="example highlight" id="example-470647ba"><a class="self-link" href="#example-470647ba"></a><c- a>const</c-> compressedReadableStream
    <c- o>=</c-> inputReadableStream<c- p>.</c->pipeThrough<c- p>(</c-><c- ow>new</c-> CompressionStream<c- p>(</c-><c- t>'gzip'</c-><c- p>));</c->
</pre>
   <h3 class="heading settled" data-level="8.2" id="example-deflate-compress"><span class="secno">8.2. </span><span class="content">Deflate-compress an ArrayBuffer to a Uint8Array</span><a class="self-link" href="#example-deflate-compress"></a></h3>
<pre class="example highlight" id="example-09e4ae49"><a class="self-link" href="#example-09e4ae49"></a><c- k>async</c-> <c- a>function</c-> compressArrayBuffer<c- p>(</c->input<c- p>)</c-> <c- p>{</c->
  <c- a>const</c-> cs <c- o>=</c-> <c- ow>new</c-> CompressionStream<c- p>(</c-><c- t>'deflate'</c-><c- p>);</c->
  <c- a>const</c-> writer <c- o>=</c-> cs<c- p>.</c->writable<c- p>.</c->getWriter<c- p>();</c->
  writer<c- p>.</c->write<c- p>(</c->input<c- p>);</c->
  writer<c- p>.</c->close<c- p>();</c->
  <c- a>const</c-> output <c- o>=</c-> <c- p>[];</c->
  <c- a>const</c-> reader <c- o>=</c-> cs<c- p>.</c->readable<c- p>.</c->getReader<c- p>();</c->
  <c- a>let</c-> totalSize <c- o>=</c-> <c- mf>0</c-><c- p>;</c->
  <c- k>while</c-> <c- p>(</c-><c- kc>true</c-><c- p>)</c-> <c- p>{</c->
    <c- a>const</c-> <c- p>{</c-> value<c- p>,</c-> done <c- p>}</c-> <c- o>=</c-> <c- k>await</c-> reader<c- p>.</c->read<c- p>();</c->
    <c- k>if</c-> <c- p>(</c->done<c- p>)</c->
      <c- k>break</c-><c- p>;</c->
    output<c- p>.</c->push<c- p>(</c->value<c- p>);</c->
    totalSize <c- o>+=</c-> value<c- p>.</c->byteLength<c- p>;</c->
  <c- p>}</c->
  <c- a>const</c-> concatenated <c- o>=</c-> <c- ow>new</c-> Uint8Array<c- p>(</c->totalSize<c- p>);</c->
  <c- a>let</c-> offset <c- o>=</c-> <c- mf>0</c-><c- p>;</c->
  <c- k>for</c-> <c- p>(</c-><c- a>const</c-> array <c- k>of</c-> output<c- p>)</c-> <c- p>{</c->
    concatenated<c- p>.</c->set<c- p>(</c->array<c- p>,</c-> offset<c- p>);</c->
    offset <c- o>+=</c-> array<c- p>.</c->byteLength<c- p>;</c->
  <c- p>}</c->
  <c- k>return</c-> concatenated<c- p>;</c->
<c- p>}</c->
</pre>
   <h3 class="heading settled" data-level="8.3" id="example-gzip-decompress"><span class="secno">8.3. </span><span class="content">Gzip-decompress a Blob to Blob</span><a class="self-link" href="#example-gzip-decompress"></a></h3>
<pre class="example highlight" id="example-f0a2126d"><a class="self-link" href="#example-f0a2126d"></a><c- a>function</c-> decompressBlob<c- p>(</c->blob<c- p>)</c-> <c- p>{</c->
  <c- a>const</c-> ds <c- o>=</c-> <c- ow>new</c-> DecompressionStream<c- p>(</c-><c- t>'gzip'</c-><c- p>);</c->
  <c- a>const</c-> decompressionStream <c- o>=</c-> blob<c- p>.</c->stream<c- p>().</c->pipeThrough<c- p>(</c->ds<c- p>);</c->
  <c- k>return</c-> <c- ow>new</c-> Response<c- p>(</c->decompressionStream<c- p>).</c->blob<c- p>();</c->
<c- p>}</c->
</pre>
   <h2 class="heading settled" data-level="9" id="acknowledgments"><span class="secno">9. </span><span class="content">Acknowledgments</span><a class="self-link" href="#acknowledgments"></a></h2>
    The editors wish to thank Domenic Denicola and Yutaka Hirano, for their support.
  </main>
<script src="https://www.w3.org/scripts/TR/2021/fixup.js"></script>
  <h2 class="no-num no-ref heading settled" id="index"><span class="content">Index</span><a class="self-link" href="#index"></a></h2>
  <h3 class="no-num no-ref heading settled" id="index-defined-here"><span class="content">Terms defined by this specification</span><a class="self-link" href="#index-defined-here"></a></h3>
  <ul class="index">
   <li><a href="#compress-and-enqueue-a-chunk">compress and enqueue a chunk</a><span>, in § 5</span>
   <li><a href="#compress-flush-and-enqueue">compress flush and enqueue</a><span>, in § 5</span>
   <li><a href="#compression-context">compression context</a><span>, in § 3</span>
   <li><a href="#compressionstream">CompressionStream</a><span>, in § 5</span>
   <li><a href="#dom-compressionstream-compressionstream">CompressionStream(format)</a><span>, in § 5</span>
   <li>
    constructor(format)