savemedia

Browser extension for saving browser-visible video when the extension can prove it is a complete video and can produce one playable final file.

There is one support contract. A path is either supported, refused with a clear reason, or not claimed. savemedia is not a DRM bypass tool and does not use a native host, yt-dlp, ffmpeg.wasm, local ffmpeg, or hidden remote services.

Supported

The release gates cover these paths with real media fixtures:

• Direct progressive .mp4, .webm, and .mkv files after headers or magic bytes confirm the container. A matching URL extension alone is only a hint.
• Plain HLS VOD with MPEG-TS segments, remuxed to one playable MP4.
• Plain HLS VOD with clear fMP4/CMAF init + media fragments, assembled to one playable MP4 after MP4 box validation.
• DRM, ClearKey/CENC, DASH, encrypted HLS, malformed fMP4/CMAF, and live HLS detection as refusal cases.
• Negative filtering for .jpg, .jpeg, .png, .gif, .webp, .css, .js, .html, standalone audio files, orphan .ts, orphan .m4s, init segments, and numbered chunk URLs.
• Alt+S command registration and best-download routing.
• Firefox Desktop runtime smoke coverage for the direct, HLS, command, and refusal paths listed in the browser evidence table.

The engine aborts partial in-memory output when a required segment fails. It must not save random chunks, fake .mp4 HTML responses, or mislabeled .ts bytes as final video.

Refused

• DASH downloads.
• Standalone audio downloads.
• HLS AES-128, SAMPLE-AES, SAMPLE-AES-CTR, ClearKey/CENC, Widevine, PlayReady, FairPlay, and other protected media paths.
• HLS Live/DVR or any playlist without EXT-X-ENDLIST.
• HLS fMP4/CMAF playlists whose init or media fragments fail MP4 box validation.
• Direct .mov, .avi, .wmv, .flv, .m4v as independent support claims. m4v may be accepted only when bytes prove it is normal MP4.
• Transcoding, size-reduction modes, arbitrary container conversion, and browser-native downloads above the in-memory safety limit.
• Unknown protocol or URL-only "best effort" downloads.

Browser Evidence

Browser target	Current evidence	Claim level
Chrome	Automated unpacked-extension Playwright suite, including direct, HLS MPEG-TS, and HLS fMP4/CMAF downloads verified with ffprobe.	Claimed after the Chrome gate passes for the release commit.
Edge	Edge zip builds; smoke:edge launches Microsoft Edge, opens the popup, checks Alt+S, downloads direct MP4, remuxes HLS MPEG-TS VOD, downloads clear HLS fMP4/CMAF, and verifies refusal fixtures.	Claimed after the Edge smoke gate passes for the release commit.
Firefox	Firefox zip builds for Firefox Desktop 140+; smoke:firefox temporarily installs dist-firefox, opens the popup, checks Alt+S, downloads direct MP4, remuxes HLS MPEG-TS VOD, downloads clear HLS fMP4/CMAF, and verifies refusal fixtures.	Claimed after Firefox lint and smoke gates pass for the release commit.

Store-readiness drafts live in docs/privacy-policy.md and docs/store-submission.md. Any store listing must match the browser evidence above and must not imply DRM, paywall, login, protected-stream, or universal download bypass.

Architecture

• packages/core: classification, DASH/DRM/HLS parsing for descriptors, dispatch decisions, retry policy, and user-facing error taxonomy.
• packages/extension: MV3 extension, popup UI, background router, passive content detection, Chromium offscreen engine host, direct downloads, and plain-HLS jobs.
• packages/extension/tests/e2e/media-fixtures: real tiny downloadable media fixtures used by Playwright and ffprobe.

Chrome execution path:

1. MAIN-world content script passively observes resource timing, media elements, MediaSource encryption probes, and EME requests. It does not monkey-patch page fetch or XMLHttpRequest.
2. ISOLATED bridge relays tagged messages to the service worker.
3. The service worker also watches network entry requests, classifies descriptors, dedupes noisy segment URLs, and starts either a direct browser download or an HLS engine job.
4. The offscreen engine fetches the selected HLS media playlist and segments, refuses unsupported layouts/encryption, remuxes MPEG-TS to MP4 or assembles validated fMP4/CMAF fragments, verifies the MP4 structure, and hands a Blob URL to chrome.downloads.download.

Development

pnpm install
pnpm --filter @savemedia/core build
pnpm -r typecheck
pnpm -r test
pnpm --filter @savemedia/extension build:chrome
pnpm --filter @savemedia/extension test:e2e
pnpm --filter @savemedia/extension smoke:edge
pnpm --filter @savemedia/extension smoke:firefox
pnpm --filter @savemedia/extension zip

pnpm verify runs typecheck, unit tests, production Chrome and Firefox builds, and the Chromium Playwright suite against the unpacked Chrome extension. Install ffmpeg/ffprobe before running media-download e2e or smoke tests.

Loading Locally

Build and load Chrome from:

pnpm --filter @savemedia/extension build:chrome

Then load packages/extension/dist-chrome as an unpacked extension.

Release zips are created by:

pnpm --filter @savemedia/extension zip

The zip task creates Chrome, Edge, Firefox, and source packages. Generated packages include LICENSE and NOTICE; do not upload stale local zips after a source or license change.

License

Apache-2.0. See LICENSE and NOTICE.

Support

Use GitHub Issues for reproducible bugs and store-review questions. Do not post credentials, cookies, private media URLs, license keys, or other secrets.