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 ChromeNot in Firefox
In Chrome 178
In Firefox 12

Unstable APIs

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

Raw Data

Quick Links:

HTTP Data

API First Browser Date Days in Limbo Notes
http.headers.Accept-CH 📋Chrome10/13/20153810
http.headers.Accept-CH.Content-DPR Chrome10/13/20153810
http.headers.Accept-CH.DPR Chrome10/13/20153810
http.headers.Accept-CH.Device-Memory Chrome9/5/20173117
http.headers.Accept-CH.Sec-CH-DPR 📋Chrome1/4/20221535
http.headers.Accept-CH.Sec-CH-Device-Memory 📋Chrome1/4/20221535
http.headers.Accept-CH.Sec-CH-UA Chrome3/2/20211843
http.headers.Accept-CH.Sec-CH-UA-Arch Chrome3/2/20211843
http.headers.Accept-CH.Sec-CH-UA-Full-Version Chrome3/2/20211843
http.headers.Accept-CH.Sec-CH-UA-Mobile Chrome3/2/20211843
http.headers.Accept-CH.Sec-CH-UA-Model Chrome3/2/20211843
http.headers.Accept-CH.Sec-CH-UA-Platform Chrome3/2/20211843
http.headers.Accept-CH.Sec-CH-UA-Platform-Version Chrome3/2/20211843
http.headers.Accept-CH.Sec-CH-Viewport-Height 📋Chrome9/2/20221294
http.headers.Accept-CH.Sec-CH-Viewport-Width 📋Chrome1/4/20221535
http.headers.Accept-CH.Sec-CH-Width 📋Chrome1/4/20221535
http.headers.Accept-CH.Viewport-Width Chrome10/13/20153810
http.headers.Accept-CH.Width Chrome10/13/20153810
http.headers.Accept-Encoding.dcb Chrome10/15/2024520
http.headers.Accept-Encoding.dcz Chrome10/15/2024520
http.headers.Access-Control-Allow-Headers.authorization_not_covered_by_wildcard Firefox7/4/2023989
http.headers.Attribution-Reporting-Eligible 📋Chrome9/12/2023919
http.headers.Attribution-Reporting-Register-Source 📋Chrome9/12/2023919
http.headers.Attribution-Reporting-Register-Trigger 📋Chrome9/12/2023919
http.headers.Attribution-Reporting-Support 📋Chrome9/12/2023919
http.headers.Authorization.authorization_removed_cross_origin 📋Firefox3/14/20231101
http.headers.Available-Dictionary 📋Chrome10/15/2024520
http.headers.Cache-Control.immutable Firefox9/20/20163467
http.headers.Clear-Site-Data.clientHints 📋Chrome9/12/2023919
http.headers.Clear-Site-Data.prefetchCache Chrome6/24/2025268
http.headers.Clear-Site-Data.prerenderCache Chrome6/24/2025268
http.headers.Content-DPR Chrome10/13/20153810
http.headers.Content-Encoding.dcb Chrome10/15/2024520
http.headers.Content-Encoding.dcz Chrome10/15/2024520
http.headers.Content-Security-Policy.block-all-mixed-content Chrome7/21/20153894
Chrome: Will be removed, see bug 40260100.Chrome Android: Will be removed, see bug 40260100.Edge: 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.fenced-frame-src 📋Chrome6/11/2024646
http.headers.Content-Security-Policy.form-action.blocks_redirects Chrome12/6/20173025
http.headers.Content-Security-Policy.require-trusted-types-for 📋Chrome5/19/20202130
http.headers.Content-Security-Policy.script-src.inline-speculation-rules Chrome2/7/20231136
http.headers.Content-Security-Policy.trusted-types 📋Chrome5/19/20202130
http.headers.Critical-CH 📋Chrome5/25/20211759
http.headers.Cross-Origin-Embedder-Policy.report-to_parameter 📋Chrome11/15/20211585
http.headers.Cross-Origin-Opener-Policy.noopener-allow-popups 📋Chrome11/12/2024492
http.headers.Cross-Origin-Opener-Policy.report-to_parameter 📋Chrome11/15/20211585
http.headers.DPR Chrome10/13/20153810
http.headers.Device-Memory Chrome9/5/20173117
Chrome: From Chrome 147, reported values are 2, 4, 8, 16, and 32.Chrome: Before Chrome 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.Chrome Android: From Chrome 147, reported values are 1, 2, 4, and 8.Chrome Android: Before Chrome 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.Edge: From Edge 147, reported values are 2, 4, 8, 16, and 32.Edge: Before Edge 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.Quest Browser: From Chrome 147, reported values are 1, 2, 4, and 8.Quest Browser: Before Chrome 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.Opera: From Opera false, reported values are 2, 4, 8, 16, and 32.Opera: Before Opera false, reported values were 0.25, 0.5, 1, 2, 4, and 8.Opera Android: From Chrome 147, reported values are 1, 2, 4, and 8.Opera Android: Before Chrome 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.Samsung Internet: From Chrome 147, reported values are 1, 2, 4, and 8.Samsung Internet: Before Chrome 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.WebView Android: From Chrome 147, reported values are 1, 2, 4, and 8.WebView Android: Before Chrome 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.
http.headers.Dictionary-ID 📋Chrome10/15/2024520
http.headers.Downlink 📋Chrome5/29/20182851
Chrome: The value is never greater than 10 Mbps, as a non-standard anti-fingerprinting measure.Chrome Android: The value is never greater than 10 Mbps, as a non-standard anti-fingerprinting measure.Edge: The value is never greater than 10 Mbps, as a non-standard anti-fingerprinting measure.Quest Browser: The value is never greater than 10 Mbps, as a non-standard anti-fingerprinting measure.Opera: The value is never greater than 10 Mbps, as a non-standard anti-fingerprinting measure.Opera Android: The value is never greater than 10 Mbps, as a non-standard anti-fingerprinting measure.Samsung Internet: The value is never greater than 10 Mbps, as a non-standard anti-fingerprinting measure.WebView Android: The value is never greater than 10 Mbps, as a non-standard anti-fingerprinting measure.
http.headers.ECT 📋Chrome5/29/20182851
http.headers.Early-Data 📋Firefox1/23/20182977
http.headers.Feature-Policy Chrome7/25/20173159
http.headers.Feature-Policy.accelerometer 📋Chrome4/17/20182893
http.headers.Feature-Policy.ambient-light-sensor 📋Chrome4/17/20182893
http.headers.Feature-Policy.attribution-reporting 📋Chrome9/12/2023919
http.headers.Feature-Policy.autoplay 📋Chrome1/23/20182977
http.headers.Feature-Policy.bluetooth 📋Chrome8/2/20221325
http.headers.Feature-Policy.browsing-topics Chrome7/18/2023975
http.headers.Feature-Policy.camera 📋Chrome1/23/20182977
http.headers.Feature-Policy.compute-pressure 📋Chrome5/14/2024674
http.headers.Feature-Policy.cross-origin-isolated 📋Chrome11/17/20201948
http.headers.Feature-Policy.deferred-fetch 📋Chrome4/1/2025352
http.headers.Feature-Policy.deferred-fetch-minimal 📋Chrome4/1/2025352
http.headers.Feature-Policy.display-capture 📋Chrome9/21/20211640
http.headers.Feature-Policy.document-domain 📋Chrome1/23/20182977
http.headers.Feature-Policy.encrypted-media 📋Chrome1/23/20182977
http.headers.Feature-Policy.fullscreen 📋Chrome10/17/20173075
http.headers.Feature-Policy.geolocation 📋Chrome1/23/20182977
http.headers.Feature-Policy.gyroscope 📋Chrome4/17/20182893
http.headers.Feature-Policy.hid 📋Chrome3/2/20211843
http.headers.Feature-Policy.identity-credentials-get 📋Chrome2/7/20231136
http.headers.Feature-Policy.idle-detection 📋Chrome9/21/20211640
http.headers.Feature-Policy.local-fonts 📋Chrome6/21/20221367
http.headers.Feature-Policy.magnetometer 📋Chrome4/17/20182893
http.headers.Feature-Policy.microphone 📋Chrome1/23/20182977
http.headers.Feature-Policy.midi 📋Chrome1/23/20182977
http.headers.Feature-Policy.otp-credentials 📋Chrome8/31/20211661
http.headers.Feature-Policy.payment 📋Chrome7/25/20173159
http.headers.Feature-Policy.picture-in-picture 📋Chrome9/4/20182753
http.headers.Feature-Policy.publickey-credentials-create 📋Chrome7/27/20202061
http.headers.Feature-Policy.publickey-credentials-get 📋Chrome7/27/20202061
http.headers.Feature-Policy.screen-wake-lock 📋Chrome7/27/20202061
http.headers.Feature-Policy.serial 📋Chrome3/2/20211843
http.headers.Feature-Policy.storage-access 📋Chrome5/2/20231052
http.headers.Feature-Policy.usb 📋Chrome7/25/20173159
http.headers.Feature-Policy.web-share 📋Chrome10/20/20201976
http.headers.Feature-Policy.wildcards Chrome11/29/20221206
http.headers.Feature-Policy.window-management 📋Chrome3/29/20221451
http.headers.Feature-Policy.xr-spatial-tracking 📋Chrome12/10/20192291
http.headers.Idempotency-Key 📋Firefox2/4/2025408
Firefox: Automatically adds a unique 64-bit key for POST requests when needed, if not set in JavaScript.
http.headers.Integrity-Policy.blocked-destinations_style 📋Firefox8/19/2025212
http.headers.Integrity-Policy-Report-Only.blocked-destinations_style 📋Firefox8/19/2025212
http.headers.NEL 📋Chrome12/4/20182662
http.headers.No-Vary-Search 📋Chrome9/30/2025170
Chrome: Before Chrome 127, speculation rules are only supported for navigational prefetch, not prerender.Chrome: Before Chrome 141, HTTP cache is not supported.Chrome Android: Before Chrome Android 127, speculation rules are only supported for navigational prefetch, not prerender.Chrome Android: Before Chrome Android 141, HTTP cache is not supported.Edge: Before Edge 127, speculation rules are only supported for navigational prefetch, not prerender.Edge: Before Edge 141, HTTP cache is not supported.Opera: Before Opera 113, speculation rules are only supported for navigational prefetch, not prerender.Opera: Before Opera 125, HTTP cache is not supported.Opera Android: Before Opera Android 84, speculation rules are only supported for navigational prefetch, not prerender.Opera Android: Before Opera Android 93, HTTP cache is not supported.Samsung Internet: Before Samsung Internet 28.0, speculation rules are only supported for navigational prefetch, not prerender.Samsung Internet: Before Samsung Internet false, HTTP cache is not supported.WebView Android: Before WebView Android 127, speculation rules are only supported for navigational prefetch, not prerender.WebView Android: Before WebView Android 141, HTTP cache is not supported.
http.headers.No-Vary-Search.http_cache 📋Chrome9/30/2025170
http.headers.No-Vary-Search.speculation_rules_prefetch 📋Chrome1/23/2024786
http.headers.No-Vary-Search.speculation_rules_prerender 📋Chrome7/23/2024604
http.headers.Observe-Browsing-Topics Chrome7/18/2023975
http.headers.Permissions-Policy 📋Chrome1/19/20211885
http.headers.Permissions-Policy.accelerometer 📋Chrome1/19/20211885
http.headers.Permissions-Policy.ambient-light-sensor 📋Chrome4/17/20182893
http.headers.Permissions-Policy.aria-notify Chrome9/30/2025170
Chrome: Not supported on ChromeOS.Chrome Android: Not supported on ChromeOS.Edge: Not supported on ChromeOS.Opera: Not supported on ChromeOS.Opera Android: Not supported on ChromeOS.WebView Android: Not supported on ChromeOS.
http.headers.Permissions-Policy.attribution-reporting 📋Chrome9/12/2023919
http.headers.Permissions-Policy.autoplay 📋Chrome1/19/20211885
http.headers.Permissions-Policy.bluetooth 📋Chrome8/2/20221325
http.headers.Permissions-Policy.browsing-topics Chrome7/18/2023975
http.headers.Permissions-Policy.camera 📋Chrome1/19/20211885
http.headers.Permissions-Policy.captured-surface-control 📋Chrome4/29/2025324
http.headers.Permissions-Policy.ch-ua-high-entropy-values 📋Chrome1/13/202665
http.headers.Permissions-Policy.compute-pressure 📋Chrome5/14/2024674
http.headers.Permissions-Policy.cross-origin-isolated 📋Chrome1/19/20211885
http.headers.Permissions-Policy.deferred-fetch 📋Chrome4/1/2025352
http.headers.Permissions-Policy.deferred-fetch-minimal 📋Chrome4/1/2025352
http.headers.Permissions-Policy.display-capture 📋Chrome9/21/20211640
http.headers.Permissions-Policy.encrypted-media 📋Chrome1/19/20211885
http.headers.Permissions-Policy.fullscreen 📋Chrome1/19/20211885
http.headers.Permissions-Policy.gamepad 📋Chrome6/21/20221367
http.headers.Permissions-Policy.geolocation 📋Chrome1/19/20211885
http.headers.Permissions-Policy.gyroscope 📋Chrome1/19/20211885
http.headers.Permissions-Policy.hid 📋Chrome3/2/20211843
http.headers.Permissions-Policy.identity-credentials-get 📋Chrome2/7/20231136
http.headers.Permissions-Policy.idle-detection 📋Chrome9/21/20211640
http.headers.Permissions-Policy.local-fonts 📋Chrome6/21/20221367
http.headers.Permissions-Policy.magnetometer 📋Chrome4/17/20182893
http.headers.Permissions-Policy.microphone 📋Chrome1/19/20211885
http.headers.Permissions-Policy.midi 📋Chrome1/19/20211885
http.headers.Permissions-Policy.on-device-speech-recognition 📋Chrome10/28/2025142
http.headers.Permissions-Policy.otp-credentials 📋Chrome8/31/20211661
http.headers.Permissions-Policy.payment 📋Chrome1/19/20211885
http.headers.Permissions-Policy.picture-in-picture 📋Chrome1/19/20211885
http.headers.Permissions-Policy.private-state-token-issuance 📋Chrome9/12/2023919
http.headers.Permissions-Policy.private-state-token-redemption 📋Chrome9/12/2023919
http.headers.Permissions-Policy.publickey-credentials-create 📋Chrome1/19/20211885
http.headers.Permissions-Policy.publickey-credentials-get 📋Chrome1/19/20211885
http.headers.Permissions-Policy.screen-wake-lock 📋Chrome1/19/20211885
http.headers.Permissions-Policy.serial 📋Chrome3/2/20211843
http.headers.Permissions-Policy.storage-access 📋Chrome5/2/20231052
http.headers.Permissions-Policy.summarizer 📋Chrome6/24/2025268
http.headers.Permissions-Policy.usb 📋Chrome1/19/20211885
http.headers.Permissions-Policy.web-share 📋Chrome1/19/20211885
http.headers.Permissions-Policy.wildcards Chrome11/29/20221206
http.headers.Permissions-Policy.window-management 📋Chrome3/29/20221451
http.headers.Permissions-Policy.xr-spatial-tracking 📋Chrome1/19/20211885
http.headers.RTT 📋Chrome5/29/20182851
Chrome: The value is never greater than 3000 ms, as a non-standard anti-fingerprinting measure.Chrome Android: The value is never greater than 3000 ms, as a non-standard anti-fingerprinting measure.Edge: The value is never greater than 3000 ms, as a non-standard anti-fingerprinting measure.Quest Browser: The value is never greater than 3000 ms, as a non-standard anti-fingerprinting measure.Opera: The value is never greater than 3000 ms, as a non-standard anti-fingerprinting measure.Opera Android: The value is never greater than 3000 ms, as a non-standard anti-fingerprinting measure.Samsung Internet: The value is never greater than 3000 ms, as a non-standard anti-fingerprinting measure.WebView Android: The value is never greater than 3000 ms, as a non-standard anti-fingerprinting measure.
http.headers.Referrer-Policy.no-referrer-when-downgrade Chrome1/25/20173340
http.headers.Referrer-Policy.origin-when-cross-origin Chrome1/25/20173340
http.headers.Referrer-Policy.unsafe-url Chrome1/25/20173340
http.headers.Retry-After 📋Chrome1/10/20134816
http.headers.Save-Data 📋Chrome3/2/20163669
http.headers.Sec-Browsing-Topics Chrome7/18/2023975
http.headers.Sec-CH-DPR 📋Chrome1/4/20221535
http.headers.Sec-CH-Device-Memory 📋Chrome1/4/20221535
Chrome: Before Chrome 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.Chrome: From Chrome 147, reported values are 2, 4, 8, 16, and 32.Chrome: Before Chrome 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.Chrome: From Chrome 147, reported values are 2, 4, 8, 16, and 32.Chrome Android: From Chrome 147, reported values are 1, 2, 4, and 8.Chrome Android: Before Chrome 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.Chrome Android: From Chrome 147, reported values are 1, 2, 4, and 8.Chrome Android: Before Chrome 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.Edge: Before Edge 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.Edge: From Edge 147, reported values are 2, 4, 8, 16, and 32.Edge: Before Edge 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.Edge: From Edge 147, reported values are 2, 4, 8, 16, and 32.Quest Browser: From Chrome 147, reported values are 1, 2, 4, and 8.Quest Browser: Before Chrome 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.Quest Browser: From Chrome 147, reported values are 1, 2, 4, and 8.Quest Browser: Before Chrome 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.Opera: Before Opera false, reported values were 0.25, 0.5, 1, 2, 4, and 8.Opera: From Opera false, reported values are 2, 4, 8, 16, and 32.Opera: Before Opera false, reported values were 0.25, 0.5, 1, 2, 4, and 8.Opera: From Opera false, reported values are 2, 4, 8, 16, and 32.Opera Android: From Chrome 147, reported values are 1, 2, 4, and 8.Opera Android: Before Chrome 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.Opera Android: From Chrome 147, reported values are 1, 2, 4, and 8.Opera Android: Before Chrome 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.Samsung Internet: From Chrome 147, reported values are 1, 2, 4, and 8.Samsung Internet: Before Chrome 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.Samsung Internet: From Chrome 147, reported values are 1, 2, 4, and 8.Samsung Internet: Before Chrome 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.WebView Android: From Chrome 147, reported values are 1, 2, 4, and 8.WebView Android: Before Chrome 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.WebView Android: From Chrome 147, reported values are 1, 2, 4, and 8.WebView Android: Before Chrome 147, reported values were 0.25, 0.5, 1, 2, 4, and 8.
http.headers.Sec-CH-Prefers-Color-Scheme 📋Chrome8/31/20211661
http.headers.Sec-CH-Prefers-Reduced-Motion 📋Chrome11/29/20221206
http.headers.Sec-CH-Prefers-Reduced-Transparency 📋Chrome10/31/2023870
http.headers.Sec-CH-UA 📋Chrome3/2/20211843
http.headers.Sec-CH-UA-Arch 📋Chrome3/2/20211843
http.headers.Sec-CH-UA-Bitness 📋Chrome8/31/20211661
http.headers.Sec-CH-UA-Form-Factors 📋Chrome4/16/2024702
http.headers.Sec-CH-UA-Full-Version 📋Chrome3/2/20211843
http.headers.Sec-CH-UA-Full-Version-List 📋Chrome2/1/20221507
http.headers.Sec-CH-UA-Mobile 📋Chrome3/2/20211843
http.headers.Sec-CH-UA-Model 📋Chrome3/2/20211843
http.headers.Sec-CH-UA-Platform 📋Chrome3/2/20211843
http.headers.Sec-CH-UA-Platform-Version 📋Chrome3/2/20211843
http.headers.Sec-CH-UA-WoW64 📋Chrome3/29/20221451
http.headers.Sec-CH-Viewport-Height 📋Chrome9/2/20221294
http.headers.Sec-CH-Viewport-Width 📋Chrome1/4/20221535
http.headers.Sec-CH-Width 📋Chrome1/4/20221535
http.headers.Sec-Fetch-Dest.fencedframe Chrome6/11/2024646
http.headers.Sec-GPC 📋Firefox11/21/2023849
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.Firefox for Android: Opt-in to GPC using the Enhanced Tracking Protection toggle 'Tell web sites not to share & sell data', or by setting the preference privacy.globalprivacycontrol.enabled to true.
http.headers.Sec-Private-State-Token 📋Chrome9/12/2023919
http.headers.Sec-Private-State-Token-Crypto-Version 📋Chrome9/12/2023919
http.headers.Sec-Private-State-Token-Lifetime 📋Chrome9/12/2023919
http.headers.Sec-Purpose.prefetch Firefox7/4/2023989
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.Sec-Purpose.speculationrules Chrome2/7/20231136
http.headers.Sec-Redemption-Record 📋Chrome9/12/2023919
http.headers.Sec-Speculation-Tags 📋Chrome4/29/2025324
http.headers.Server-Timing.trailer Firefox12/10/20192291
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 📋Chrome6/5/20173209
http.headers.Snapshot-Content-Location Chrome12/6/20173025
http.headers.Speculation-Rules 📋Chrome1/23/2024786
http.headers.Supports-Loading-Mode 📋Chrome1/10/20231164
http.headers.Supports-Loading-Mode.credentialed-prerender 📋Chrome1/10/20231164
http.headers.Supports-Loading-Mode.fenced-frame 📋Chrome9/12/2023919
http.headers.Trailer 📋Firefox12/10/20192291
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.Use-As-Dictionary 📋Chrome10/15/2024520
http.headers.Viewport-Width Chrome10/13/20153810
http.headers.Width Chrome10/13/20153810
http.mixed-content.private_network_access 📋Chrome6/24/2025268
http.status.425 📋Firefox1/23/20182977