Not yet stable

For a given set of browsers, what APIs are not yet in all of them.

Example Comparisons
Browsers
Features

Summary

A count of the number of APIs are in Browser X but not in Browser Y.
Not in FirefoxNot in Safari
In Firefox 28
In Safari 5

Unstable APIs

Below is a list of features that are not in all of Firefox and Safari

Raw Data

Quick Links:

HTTP Data

API First Browser Date Days in Limbo Notes
http.headers.Access-Control-Allow-Headers.authorization_not_covered_by_wildcard Firefox7/4/20231125
http.headers.Authorization.Digest.SHA-256 Firefox10/5/20211762
http.headers.Clear-Site-Data.cache 📋Safari9/18/20231049
http.headers.Content-Encoding.zstd 📋Firefox5/14/2024810
http.headers.Content-Security-Policy.block-all-mixed-content Safari9/20/20163603
Chrome: Will be removed, see bug 40260100.Chrome Android: Will be removed, see bug 40260100.Quest Browser: Will be removed, see bug 40260100.Opera: Will be removed, see bug 40260100.Opera Android: Will be removed, see bug 40260100.Samsung Internet: Will be removed, see bug 40260100.WebView Android: Will be removed, see bug 40260100.
http.headers.Content-Security-Policy.form-action.blocks_redirects Safari4/12/20183034
http.headers.Content-Security-Policy.prefetch-src Safari1/23/20231287
http.headers.Cross-Origin-Embedder-Policy.credentialless 📋Firefox10/24/20231013
http.headers.DNT Firefox3/22/20115612
http.headers.Early-Data 📋Firefox1/23/20183113
http.headers.Priority 📋Firefox7/9/2024754
http.headers.Report-To Firefox9/3/2024698
http.headers.Reporting-Endpoints 📋Firefox9/3/2024698
http.headers.Sec-GPC 📋Firefox11/21/2023985
Firefox: Opt-in to GPC using the Website Privacy Preference setting (about:preferences#privacy) checkbox 'Tell websites not to sell or share my data', or by setting the preference privacy.globalprivacycontrol.enabled to true.
http.headers.Sec-Purpose 📋Firefox7/4/20231125
http.headers.Sec-Purpose.prefetch Firefox7/4/20231125
Chrome: Doesn't support Sec-Purpose for <link rel="prefetch">. In Chrome, the legacy Purpose: prefetch header is used to indicate a link request is a prefetch. See bug 40236973.Chrome Android: Doesn't support Sec-Purpose for <link rel="prefetch">. In Chrome Android, the legacy Purpose: prefetch header is used to indicate a link request is a prefetch. See bug 40236973.Edge: Doesn't support Sec-Purpose for <link rel="prefetch">. In Edge, the legacy Purpose: prefetch header is used to indicate a link request is a prefetch. See bug 40236973.Firefox: Sec-Purpose: prefetch replaces the non-standard X-moz: prefetch header that was used to indicate a link prefetch request in earlier versions.Firefox: Prefetch requests should also include the header Accept header string for navigations, but Accept: */* is sent instead.Firefox for Android: Sec-Purpose: prefetch replaces the non-standard X-moz: prefetch header that was used to indicate a link prefetch request in earlier versions.Firefox for Android: Prefetch requests should also include the header Accept header string for navigations, but Accept: */* is sent instead.Quest Browser: Doesn't support Sec-Purpose for <link rel="prefetch">. In Quest Browser, the legacy Purpose: prefetch header is used to indicate a link request is a prefetch. See bug 40236973.Opera: Doesn't support Sec-Purpose for <link rel="prefetch">. In Opera, the legacy Purpose: prefetch header is used to indicate a link request is a prefetch. See bug 40236973.Samsung Internet: Doesn't support Sec-Purpose for <link rel="prefetch">. In Samsung Internet, the legacy Purpose: prefetch header is used to indicate a link request is a prefetch. See bug 40236973.WebView Android: Doesn't support Sec-Purpose for <link rel="prefetch">. In WebView Android, the legacy Purpose: prefetch header is used to indicate a link request is a prefetch. See bug 40236973.
http.headers.Server-Timing.trailer Firefox12/10/20192427
Firefox: Only the Server-Timing header is a recognized trailer, and it is only exposed to DevTools in the network Timing tab (bug 1403051). Developers cannot access trailers via the Fetch API or XHR.Firefox for Android: Only the Server-Timing header is a recognized trailer, and it is only exposed to DevTools in the network Timing tab (bug 1403051). Developers cannot access trailers via the Fetch API or XHR.
http.headers.Service-Worker-Navigation-Preload 📋Safari3/14/20221602
http.headers.Set-Cookie.Partitioned 📋Firefox10/1/2024670
http.headers.Set-Cookie.SameSite.Lax_default Firefox9/3/20192525
http.headers.Set-Cookie.SameSite.none_requires_secure Firefox10/1/2024670
http.headers.Set-Cookie.SameSite.schemeful Firefox7/28/20202196
http.headers.Trailer 📋Firefox12/10/20192427
Firefox: Only the Server-Timing header is a recognized trailer, and it is only exposed to DevTools in the network Timing tab (bug 1403051). Developers cannot access trailers via the Fetch API or XHR.Firefox for Android: Only the Server-Timing header is a recognized trailer, and it is only exposed to DevTools in the network Timing tab (bug 1403051). Developers cannot access trailers via the Fetch API or XHR.
http.headers.WWW-Authenticate.Digest.SHA-256 Firefox10/5/20211762
http.headers.X-DNS-Prefetch-Control Firefox10/24/20067222
http.mixed-content.allow_file_urls 📋Firefox8/6/20134744
http.mixed-content.allow_localhost_url 📋Firefox12/15/20202056
http.mixed-content.allow_loopback_url 📋Firefox8/8/20173281
http.mixed-content.auto_upgrade_images 📋Firefox6/11/2024782
Firefox: Set security.mixed_content.upgrade_display_content preference to true to allow HTTP fetching and display of upgradable content.Firefox: Set security.mixed_content.block_display_content preference to true to block all mixed content.Firefox for Android: Set security.mixed_content.upgrade_display_content preference to true to allow HTTP fetching and display of upgradable content.Firefox for Android: Set security.mixed_content.block_display_content preference to true to block all mixed content.
http.mixed-content.auto_upgrade_video_audio 📋Firefox6/11/2024782
Firefox: Set security.mixed_content.upgrade_display_content preference to true to allow HTTP fetching and display of upgradable content.Firefox: Set security.mixed_content.block_display_content preference to true to block all mixed content.Firefox for Android: Set security.mixed_content.upgrade_display_content preference to true to allow HTTP fetching and display of upgradable content.Firefox for Android: Set security.mixed_content.block_display_content preference to true to block all mixed content.
http.mixed-content.block_mixed_downloads 📋Firefox7/13/20211846
http.status.103.preload Firefox2/20/2024894
http.status.425 📋Firefox1/23/20183113