CORS: Incorrect Status Code for OPTIONS endpoint #36592
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[WIP] Update ASP.NET Core web hosting documentation
Initial analysis plan for issue #36526
Jan 8, 2026
tdykstra
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Pull request overview
Updates the CORS documentation to correct the expected HTTP status code returned when an ASP.NET Core CORS preflight (OPTIONS) request is denied, aligning the article with observed middleware behavior and the linked issue report.
Changes:
- Updated two statements in the CORS article to indicate denied preflight requests return
204 No Content(instead of200 OK). - Kept the existing guidance that denied preflight responses omit CORS headers, causing the browser to block the cross-origin request.
| * [Access-Control-Request-Headers](https://developer.mozilla.org/docs/Web/HTTP/Headers/Access-Control-Allow-Headers): A list of request headers that the app sets on the actual request. As stated earlier, this doesn't include headers that the browser sets, such as `User-Agent`. | ||
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| If the preflight request is denied, the app returns a `200 OK` response but doesn't set the CORS headers. Therefore, the browser doesn't attempt the cross-origin request. For an example of a denied preflight request, see the [Test CORS](#testc6) section of this document. | ||
| If the preflight request is denied, the app returns a `204 No Content` response but doesn't set the CORS headers. Therefore, the browser doesn't attempt the cross-origin request. For an example of a denied preflight request, see the [Test CORS](#testc6) section of this document. |
tdykstra
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May 12, 2026
wadepickett
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May 12, 2026
| * [Access-Control-Request-Headers](https://developer.mozilla.org/docs/Web/HTTP/Headers/Access-Control-Allow-Headers): A list of request headers that the app sets on the actual request. As stated earlier, this doesn't include headers that the browser sets, such as `User-Agent`. | ||
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| If the preflight request is denied, the app returns a `200 OK` response but doesn't set the CORS headers. Therefore, the browser doesn't attempt the cross-origin request. For an example of a denied preflight request, see the [Test CORS](#testc6) section of this document. | ||
| If the preflight request is denied, the app returns a `204 No Content` response but doesn't set the CORS headers. Therefore, the browser doesn't attempt the cross-origin request. For an example of a denied preflight request, see the [Test CORS](#testc6) section of this document. |
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@tdykstra , Line 250 uses an astrisk around the reponse and this ilne 367 uses backticks around the "returns a 204 No Content response". Should both cases use backticks?
wadepickett
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@tdykstra, looks great! Only a minor item to look at regarding backticks around 204 No Content. Approved.
Update the date for the CORS documentation.
Replace asterisks with backticks for ` 204 new content` Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
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Fixes #36526
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