Time to Stable

For a given set of browsers, what APIs are in all of them and how many days it take for the API to land in the first browser to the last.

Example Comparisons
Browsers
Features

Summary

A count of the number of APIs that landed in A first and B last.
Last in ChromeLast in Firefox
First in Chrome 96
First in Firefox 99

Average time for an API to become available across Chrome and Firefox

195 APIs took an average of 881.42 days to become available to use.

API breakdown:

Average time to landing by year of first landing

If a feature landed in the earliest browser in 20XX it took Y days on average to become available in the last browser (when considering Chrome and Firefox). TTA (time to available).
HTTP APIsHTTP TTA
2004 611493.00
2006 51107.00
2008 22072.00
2009 8209.00
2010 4427.75
2011 6175.00
2012 21344.00
2013 17742.00
2014 1476.00
2015 9321.78
2016 11325.45
2017 14538.57
2018 81371.00
2019 13681.69
2020 8724.50
2021 6771.50
2022 7535.00
2023 3480.67
2024 365.33
2025 7180.00

The Tortoise and the Hare

There is a natural tension on the web with respect to browser engines. Every engine has their own set of priorities which define the level of investment that they choose to make and on which areas they choose to make it.

A developer naturally wants their experiences to be available to the widest audience possible and these differing priorities create an unevenness on the platform (a lumpiness) making it harder for developers to build experiences that work everywhere.

This section highlights where browsers are pushing and pulling on the platform.

Sprinters

This table is designed to show which browsers are pushing on the platform the most.

Adding features to quickly is not always desired because developers are unlikely to adopt those features in their sites or apps.

For a given year, if a feature landed in Browser X first, how many days it take on average to be available in Chrome and Firefox. TTA (time to available).
Year HTTPHTTP TTA
2004
  Firefox 611493.00
2006
  Firefox 51107.00
2008
  Chrome 13967.00
  Firefox 1177.00
2009
  Firefox 8209.00
2010
  Chrome 4427.75
2011
  Firefox 1595.00
  Chrome 591.00
2012
  Chrome 11959.00
  Firefox 1729.00
2013
  Chrome 14404.50
  Firefox 32317.00
2014
  Chrome 1476.00
2015
  Firefox 2221.50
  Chrome 7350.43
2016
  Firefox 6158.33
  Chrome 5526.00
2017
  Chrome 10614.00
  Firefox 4350.00
2018
  Chrome 61527.17
  Firefox 2902.50
2019
  Chrome 12725.67
  Firefox 1154.00
2020
  Chrome 7785.00
  Firefox 1301.00
2021
  Firefox 3473.67
  Chrome 31069.33
2022
  Chrome 7535.00
2023
  Chrome 3480.67
2024
  Chrome 365.33
2025
  Chrome 7180.00

Plodders

This table is designed to show which browsers are pulling on the platform the most.

For a feature that first landed in year X, how many days did it take on average for the last browser to catch up across Chrome and Firefox. TTA (time to available).
Year HTTP countHTTP TTA
2004
  Chrome 611493.00
2006
  Chrome 51107.00
2008
  Firefox 13967.00
  Chrome 1177.00
2009
  Chrome 8209.00
2010
  Firefox 4427.75
2011
  Chrome 1595.00
  Firefox 591.00
2012
  Firefox 11959.00
  Chrome 1729.00
2013
  Firefox 14404.50
  Chrome 32317.00
2014
  Firefox 1476.00
2015
  Chrome 2221.50
  Firefox 7350.43
2016
  Chrome 6158.33
  Firefox 5526.00
2017
  Firefox 10614.00
  Chrome 4350.00
2018
  Firefox 61527.17
  Chrome 2902.50
2019
  Firefox 12725.67
  Chrome 1154.00
2020
  Firefox 7785.00
  Chrome 1301.00
2021
  Chrome 3473.67
  Firefox 31069.33
2022
  Firefox 7535.00
2023
  Firefox 3480.67
2024
  Firefox 365.33
2025
  Firefox 7180.00

Stable APIs

Below is a list of features that are in Chrome and Firefox

Raw Data

Quick Links:

HTTP Data

API First Browser Date Last Browser Date Days Notes
http.data-url 📋Firefox10/24/2006 Chrome1/25/20101189
Edge: Before Edge 79, the maximum size supported is 4GB.Internet Explorer: Since Internet Explorer 9, the maximum size supported is 4GB.Internet Explorer: In Internet Explorer 8, the maximum size supported is 32kB.
http.data-url.css_files Firefox10/24/2006 Chrome1/25/20101189
http.data-url.html_files Firefox10/24/2006 Chrome1/25/20101189
http.data-url.js_files Firefox10/24/2006 Chrome1/25/20101189
http.data-url.top_level_navigation_blocked Chrome7/25/2017 Firefox3/13/2018231
http.headers.Accept 📋Firefox11/9/2004 Chrome12/11/20081493
Firefox: In Firefox 66, the default Accept header value changed to */*.Firefox for Android: In Firefox for Android 66, the default Accept header value changed to */*.
http.headers.Accept-Encoding 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Accept-Encoding.br 📋Firefox1/26/2016 Chrome4/13/201678
Safari: Unsupported before macOS 10.13 High Sierra.
http.headers.Accept-Encoding.zstd 📋Chrome3/19/2024 Firefox5/14/202456
Safari: Before macOS 26.3 Tahoe, this header value is not sent.
http.headers.Accept-Language 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Accept-Ranges 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Access-Control-Allow-Credentials 📋Firefox6/30/2009 Chrome1/25/2010209
http.headers.Access-Control-Allow-Headers 📋Firefox6/30/2009 Chrome1/25/2010209
http.headers.Access-Control-Allow-Headers.wildcard Chrome12/6/2017 Firefox9/3/2019636
http.headers.Access-Control-Allow-Methods 📋Firefox6/30/2009 Chrome1/25/2010209
http.headers.Access-Control-Allow-Methods.wildcard Chrome12/6/2017 Firefox9/3/2019636
http.headers.Access-Control-Allow-Origin 📋Firefox6/30/2009 Chrome1/25/2010209
http.headers.Access-Control-Expose-Headers 📋Firefox6/30/2009 Chrome1/25/2010209
http.headers.Access-Control-Expose-Headers.wildcard Chrome3/6/2018 Firefox9/3/2019546
http.headers.Access-Control-Max-Age 📋Firefox6/30/2009 Chrome1/25/2010209
http.headers.Access-Control-Request-Headers 📋Firefox6/30/2009 Chrome1/25/2010209
http.headers.Access-Control-Request-Method 📋Firefox6/30/2009 Chrome1/25/2010209
http.headers.Activate-Storage-Access 📋Chrome2/4/2025 Firefox1/13/2026343
http.headers.Age 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Alt-Svc 📋Firefox5/12/2015 Chrome7/20/2016435
Firefox: Only supports draft-04Firefox for Android: Only supports draft-04
http.headers.Authorization 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Authorization.Basic 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Authorization.Digest 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Authorization.Digest.SHA-256 Firefox10/5/2021 Chrome9/12/2023707
http.headers.Authorization.Digest.md5 Firefox11/9/2004 Chrome12/11/20081493
http.headers.Authorization.NTLM Firefox11/9/2004 Chrome12/11/20081493
http.headers.Authorization.Negotiate 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Cache-Control 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Cache-Control.stale-while-revalidate 📋Chrome6/4/2019 Firefox7/9/201935
http.headers.Clear-Site-Data 📋Chrome9/5/2017 Firefox10/23/2018413
http.headers.Clear-Site-Data.cache 📋Chrome3/6/2018 Firefox4/29/20252611
Chrome: Setting this value may increase response duration (see bug 40233601.Chrome: Setting this value may prevent a page from fully load (see bug 41343050.Chrome Android: Setting this value may increase response duration (see bug 40233601.Chrome Android: Setting this value may prevent a page from fully load (see bug 41343050.Edge: Setting this value may increase response duration (see bug 40233601.Quest Browser: Setting this value may increase response duration (see bug 40233601.Opera: Setting this value may increase response duration (see bug 40233601.Opera: Setting this value may prevent a page from fully load (see bug 41343050.Opera Android: Setting this value may increase response duration (see bug 40233601.Opera Android: Setting this value may prevent a page from fully load (see bug 41343050.Samsung Internet: Setting this value may increase response duration (see bug 40233601.WebView Android: Setting this value may increase response duration (see bug 40233601.WebView Android: Setting this value may prevent a page from fully load (see bug 41343050.
http.headers.Clear-Site-Data.cookies 📋Chrome9/5/2017 Firefox10/23/2018413
http.headers.Clear-Site-Data.secure_context_required Chrome9/5/2017 Firefox10/23/2018413
http.headers.Clear-Site-Data.storage 📋Chrome9/5/2017 Firefox10/23/2018413
http.headers.Clear-Site-Data.wildcard 📋Firefox10/23/2018 Chrome9/12/20231785
http.headers.Connection 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Content-Disposition 📋Firefox11/9/2004 Chrome12/11/20081493
Chrome: When saving documents, the document title is used instead of the filename parameter if the disposition type is inline. See bug 352093465.Chrome Android: When saving documents, the document title is used instead of the filename parameter if the disposition type is inline. See bug 352093465.Firefox: From version 82, if an <a> element's download attribute is set (for a same-origin URL) then the inline directive is ignored. Earlier versions did not match the specification and respected the header directive over the attribute. See bug 1658877.Firefox for Android: From version 82, if an <a> element's download attribute is set (for a same-origin URL) then the inline directive is ignored. Earlier versions did not match the specification and respected the header directive over the attribute. See bug 1658877.Quest Browser: When saving documents, the document title is used instead of the filename parameter if the disposition type is inline. See bug 352093465.Opera: When saving documents, the document title is used instead of the filename parameter if the disposition type is inline. See bug 352093465.Opera Android: When saving documents, the document title is used instead of the filename parameter if the disposition type is inline. See bug 352093465.Safari: When saving documents, the document title is used instead of the filename parameter if the disposition type is inline. See bug 18384.Safari on iOS: When saving documents, the document title is used instead of the filename parameter if the disposition type is inline. See bug 18384.Samsung Internet: When saving documents, the document title is used instead of the filename parameter if the disposition type is inline. See bug 352093465.WebView Android: When saving documents, the document title is used instead of the filename parameter if the disposition type is inline. See bug 352093465.WebView on iOS: When saving documents, the document title is used instead of the filename parameter if the disposition type is inline. See bug 18384.
http.headers.Content-Encoding 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Content-Encoding.br 📋Firefox1/26/2016 Chrome4/13/201678
Safari: Unsupported before macOS 10.13 High Sierra.
http.headers.Content-Encoding.zstd 📋Chrome3/19/2024 Firefox5/14/202456
Safari: Before macOS 26.3 Tahoe, Safari cannot decode Zstandard responses.
http.headers.Content-Language 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Content-Length 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Content-Length.cors_response_safelist Chrome7/30/2019 Firefox3/23/2021602
http.headers.Content-Location 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Content-Range 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Content-Security-Policy 📋Chrome2/21/2013 Firefox8/6/2013166
Internet Explorer: Only supporting 'sandbox' directive.
http.headers.Content-Security-Policy.base-uri 📋Firefox1/13/2015 Chrome1/21/20158
http.headers.Content-Security-Policy.child-src 📋Chrome1/21/2015 Firefox3/8/2016412
http.headers.Content-Security-Policy.connect-src 📋Chrome2/21/2013 Firefox11/15/20161363
Firefox: Before Firefox 50, ping attributes of <a> elements weren't covered by connect-src.
http.headers.Content-Security-Policy.default-src 📋Chrome2/21/2013 Firefox8/6/2013166
http.headers.Content-Security-Policy.font-src 📋Chrome2/21/2013 Firefox8/6/2013166
http.headers.Content-Security-Policy.form-action 📋Chrome1/21/2015 Firefox2/24/201534
http.headers.Content-Security-Policy.frame-ancestors 📋Chrome1/21/2015 Firefox1/23/20181098
Firefox: Before Firefox 58, frame-ancestors is ignored in Content-Security-Policy-Report-Only.Firefox for Android: Before Firefox for Android 58, frame-ancestors is ignored in Content-Security-Policy-Report-Only.
http.headers.Content-Security-Policy.frame-src 📋Chrome2/21/2013 Firefox8/6/2013166
http.headers.Content-Security-Policy.img-src 📋Chrome2/21/2013 Firefox8/6/2013166
http.headers.Content-Security-Policy.manifest-src 📋Chrome1/21/2015 Firefox9/22/2015244
http.headers.Content-Security-Policy.media-src 📋Chrome2/21/2013 Firefox8/6/2013166
http.headers.Content-Security-Policy.meta-element-support Chrome2/21/2013 Firefox3/8/20161111
http.headers.Content-Security-Policy.object-src 📋Chrome2/21/2013 Firefox8/6/2013166
http.headers.Content-Security-Policy.report-sample Chrome6/5/2017 Firefox10/23/2018505
http.headers.Content-Security-Policy.report-to 📋Chrome10/16/2018 Firefox9/3/20242149
http.headers.Content-Security-Policy.report-uri 📋Chrome2/21/2013 Firefox8/6/2013166
http.headers.Content-Security-Policy.sandbox 📋Chrome2/21/2013 Firefox11/15/20161363
http.headers.Content-Security-Policy.script-src 📋Chrome2/21/2013 Firefox8/6/2013166
http.headers.Content-Security-Policy.script-src.external_scripts 📋Chrome6/5/2017 Firefox8/1/20232248
http.headers.Content-Security-Policy.script-src.wasm-unsafe-eval Chrome1/4/2022 Firefox6/28/2022175
http.headers.Content-Security-Policy.script-src-attr 📋Chrome6/4/2019 Firefox12/13/20221288
http.headers.Content-Security-Policy.script-src-elem 📋Chrome6/4/2019 Firefox12/13/20221288
http.headers.Content-Security-Policy.strict-dynamic Chrome7/20/2016 Firefox3/7/2017230
http.headers.Content-Security-Policy.style-src 📋Chrome2/21/2013 Firefox8/6/2013166
http.headers.Content-Security-Policy.style-src-attr 📋Chrome6/4/2019 Firefox12/13/20221288
http.headers.Content-Security-Policy.style-src-elem 📋Chrome6/4/2019 Firefox12/13/20221288
Safari: The style-src-elem directive was parsed, but had no effect. See bug 276931.Safari on iOS: The style-src-elem directive was parsed, but had no effect. See bug 276931.WebView on iOS: The style-src-elem directive was parsed, but had no effect. See bug 276931.
http.headers.Content-Security-Policy.unsafe-hashes Chrome9/4/2018 Firefox1/17/20231596
http.headers.Content-Security-Policy.upgrade-insecure-requests 📋Chrome5/19/2015 Firefox11/3/2015168
http.headers.Content-Security-Policy.worker-src 📋Chrome6/5/2017 Firefox1/23/2018232
Chrome: Chrome 59 and higher skips the deprecated child-src directive.Chrome Android: Chrome Android 59 and higher skips the deprecated child-src directive.Quest Browser: Quest Browser 5.0 and higher skips the deprecated child-src directive.Opera: Opera 46 and higher skips the deprecated child-src directive.Opera Android: Opera Android 43 and higher skips the deprecated child-src directive.WebView Android: WebView Android 59 and higher skips the deprecated child-src directive.
http.headers.Content-Security-Policy.worker_support Firefox11/15/2016 Chrome1/25/201771
http.headers.Content-Security-Policy-Report-Only 📋Chrome2/21/2013 Firefox8/6/2013166
http.headers.Content-Type 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Cookie 📋Firefox11/9/2004 Chrome12/11/20081493
Safari: Cookies with Secure flag are not sent to unsecured http://localhost/ endpoints. See bug 281149.Safari on iOS: Cookies with Secure flag are not sent to unsecured http://localhost/ endpoints. See bug 281149.WebView on iOS: Cookies with Secure flag are not sent to unsecured http://localhost/ endpoints. See bug 281149.
http.headers.Cross-Origin-Embedder-Policy 📋Chrome5/19/2020 Firefox7/28/202070
http.headers.Cross-Origin-Embedder-Policy.credentialless 📋Chrome11/15/2021 Firefox10/24/2023708
http.headers.Cross-Origin-Opener-Policy 📋Chrome5/19/2020 Firefox7/28/202070
http.headers.Cross-Origin-Resource-Policy 📋Chrome3/12/2019 Firefox3/10/2020364
Chrome: Until version 75, downloads for files with this header would fail in Chrome. See bug 41452948.Chrome: From version 80 to 85, linearized PDFs served inline with this header fail to render properly. See bug 40127935. From version 86, partial PDF loading is disabled.Chrome Android: Until version 75, downloads for files with this header would fail in Chrome Android. See bug 41452948.Chrome Android: From version 80 to 85, linearized PDFs served inline with this header fail to render properly. See bug 40127935. From version 86, partial PDF loading is disabled.Quest Browser: Until version 7.0, downloads for files with this header would fail in Quest Browser. See bug 41452948.Quest Browser: From version 9.0 to 85, linearized PDFs served inline with this header fail to render properly. See bug 40127935. From version 12.0, partial PDF loading is disabled.Opera: Until version 62, downloads for files with this header would fail in Opera. See bug 41452948.Opera: From version 67 to 85, linearized PDFs served inline with this header fail to render properly. See bug 40127935. From version 72, partial PDF loading is disabled.Opera Android: Until version 54, downloads for files with this header would fail in Opera Android. See bug 41452948.Opera Android: From version 57 to 85, linearized PDFs served inline with this header fail to render properly. See bug 40127935. From version 61, partial PDF loading is disabled.WebView Android: Until version 75, downloads for files with this header would fail in WebView Android. See bug 41452948.WebView Android: From version 80 to 85, linearized PDFs served inline with this header fail to render properly. See bug 40127935. From version 86, partial PDF loading is disabled.
http.headers.DNT Firefox3/22/2011 Chrome11/6/2012595
http.headers.Date 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.ETag 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Expires 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.From 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Host 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.If-Match 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.If-Modified-Since 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.If-None-Match 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.If-Range 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.If-Unmodified-Since 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Integrity-Policy 📋Chrome6/24/2025 Firefox11/11/2025140
Firefox: Reporting endpoints are ignored (violations are logged to console).Firefox for Android: Reporting endpoints are ignored (violations are logged to console).
http.headers.Integrity-Policy.blocked-destinations_script 📋Chrome6/24/2025 Firefox11/11/2025140
http.headers.Integrity-Policy-Report-Only 📋Chrome6/24/2025 Firefox11/11/2025140
Firefox: Reporting endpoints are ignored (violations are logged to console).Firefox for Android: Reporting endpoints are ignored (violations are logged to console).
http.headers.Integrity-Policy-Report-Only.blocked-destinations_script 📋Chrome6/24/2025 Firefox11/11/2025140
http.headers.Keep-Alive 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Last-Modified 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Link 📋Chrome6/21/2022 Firefox11/21/2023518
http.headers.Link.fetchpriority 📋Chrome6/21/2022 Firefox10/29/2024861
http.headers.Location 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Origin 📋Chrome12/11/2008 Firefox10/22/20193967
Edge: Not sent with POST requestsFirefox: Not sent with POST requests, see bug 446344.Firefox for Android: Not sent with POST requests, see bug 446344.
http.headers.Origin-Agent-Cluster 📋Chrome4/13/2021 Firefox4/29/20251477
http.headers.Pragma 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Priority 📋Chrome4/16/2024 Firefox7/9/202484
http.headers.Proxy-Authenticate 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Range 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Range.cors_safe Chrome3/1/2022 Firefox8/29/2023546
http.headers.Referer 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Referer.length_limit_4096B Chrome9/10/2019 Firefox10/22/201942
http.headers.Referrer-Policy 📋Firefox11/15/2016 Chrome1/25/201771
http.headers.Referrer-Policy.default_strict-origin-when-cross-origin Chrome8/25/2020 Firefox3/23/2021210
http.headers.Referrer-Policy.same-origin Firefox3/7/2017 Chrome9/5/2017182
http.headers.Referrer-Policy.strict-origin Firefox3/7/2017 Chrome9/5/2017182
http.headers.Referrer-Policy.strict-origin-when-cross-origin Firefox3/7/2017 Chrome9/5/2017182
http.headers.Refresh 📋Firefox11/9/2004 Chrome12/11/20081493
Firefox: From version 136 the HTTP Referer header is sent following a refresh that redirects to another page (if permitted)Firefox for Android: From version 136 the HTTP Referer header is sent following a refresh that redirects to another page (if permitted)
http.headers.Report-To Chrome10/16/2018 Firefox9/3/20242149
http.headers.Reporting-Endpoints 📋Chrome11/15/2021 Firefox9/3/20241023
http.headers.Sec-Fetch-Dest 📋Chrome2/4/2020 Firefox7/13/2021525
http.headers.Sec-Fetch-Mode 📋Chrome7/30/2019 Firefox7/13/2021714
http.headers.Sec-Fetch-Site 📋Chrome7/30/2019 Firefox7/13/2021714
http.headers.Sec-Fetch-Storage-Access 📋Chrome2/4/2025 Firefox1/13/2026343
http.headers.Sec-Fetch-User 📋Chrome7/30/2019 Firefox7/13/2021714
http.headers.Sec-Purpose 📋Chrome2/7/2023 Firefox7/4/2023147
http.headers.Sec-WebSocket-Accept 📋Chrome12/13/2011 Firefox3/13/201291
http.headers.Sec-WebSocket-Extensions 📋Chrome12/13/2011 Firefox3/13/201291
http.headers.Sec-WebSocket-Key 📋Chrome12/13/2011 Firefox3/13/201291
http.headers.Sec-WebSocket-Protocol 📋Chrome12/13/2011 Firefox3/13/201291
http.headers.Sec-WebSocket-Version 📋Chrome12/13/2011 Firefox3/13/201291
http.headers.Server 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Server-Timing 📋Chrome3/6/2018 Firefox6/26/2018112
http.headers.Service-Worker 📋Chrome10/7/2014 Firefox1/26/2016476
http.headers.Service-Worker-Allowed 📋Chrome4/14/2015 Firefox8/11/2015119
http.headers.Set-Cookie 📋Firefox11/9/2004 Chrome12/11/20081493
Safari: Cookies with Secure flag are not sent to unsecured http://localhost/ endpoints. See bug 281149.Safari on iOS: Cookies with Secure flag are not sent to unsecured http://localhost/ endpoints. See bug 281149.WebView on iOS: Cookies with Secure flag are not sent to unsecured http://localhost/ endpoints. See bug 281149.
http.headers.Set-Cookie.HttpOnly Firefox6/17/2008 Chrome12/11/2008177
http.headers.Set-Cookie.Max-Age Firefox11/9/2004 Chrome12/11/20081493
http.headers.Set-Cookie.Partitioned 📋Chrome5/30/2023 Firefox7/22/2025784
http.headers.Set-Cookie.SameSite 📋Chrome5/25/2016 Firefox5/9/2018714
Safari: Safari 13 on macOS 10.14 (Mojave), treats SameSite=None and invalid values as Strict. This is fixed in version 10.15 (Catalina) and later.Safari: Treats SameSite=None and invalid values as Strict in macOS before 10.15 Catalina. See bug 198181.Safari on iOS: Treats SameSite=None and invalid values as Strict in iOS before 13. See bug 198181.WebView on iOS: Treats SameSite=None and invalid values as Strict in iOS before 13. See bug 198181.
http.headers.Set-Cookie.SameSite.Lax Chrome5/25/2016 Firefox5/9/2018714
http.headers.Set-Cookie.SameSite.Lax_default Firefox9/3/2019 Chrome2/4/2020154
http.headers.Set-Cookie.SameSite.None Firefox5/9/2018 Chrome5/29/201820
Chrome: Rejects cookies with SameSite=None. See SameSite=None: Known Incompatible Clients.Chrome Android: Rejects cookies with SameSite=None. See SameSite=None: Known Incompatible Clients.Quest Browser: Rejects cookies with SameSite=None. See SameSite=None: Known Incompatible Clients.Opera: Rejects cookies with SameSite=None. See SameSite=None: Known Incompatible Clients.Opera Android: Rejects cookies with SameSite=None. See SameSite=None: Known Incompatible Clients.Safari: Not supported before macOS version 10.15 (Catalina).Samsung Internet: Rejects cookies with SameSite=None. See SameSite=None: Known Incompatible Clients.WebView Android: Rejects cookies with SameSite=None. See SameSite=None: Known Incompatible Clients.
http.headers.Set-Cookie.SameSite.Strict Chrome5/25/2016 Firefox5/9/2018714
http.headers.Set-Cookie.SameSite.none_requires_secure Chrome2/4/2020 Firefox10/1/20241701
http.headers.Set-Cookie.SameSite.schemeful Firefox7/28/2020 Chrome5/25/2021301
http.headers.Set-Cookie.host_secure_prefixes Chrome3/2/2016 Firefox11/15/2016258
http.headers.Set-Cookie.http_host-http_prefixes Chrome9/2/2025 Firefox9/16/202514
Firefox: __Host-Http- is supported under its original name __HostHttp-. See bug 1982555.Firefox for Android: __Host-Http- is supported under its original name __HostHttp-. See bug 1982555.
http.headers.Set-Login 📋Chrome12/5/2023 Firefox4/29/2025511
http.headers.SourceMap 📋Chrome3/28/2012 Firefox8/8/20171959
Chrome: Not supported for ECMAScript Modules (<script type="module">). See bug 40854862.Chrome Android: Not supported for ECMAScript Modules (<script type="module">). See bug 40854862.Edge: Not supported for ECMAScript Modules (<script type="module">). See bug 40854862.Quest Browser: Not supported for ECMAScript Modules (<script type="module">). See bug 40854862.Opera: Not supported for ECMAScript Modules (<script type="module">). See bug 40854862.Opera Android: Not supported for ECMAScript Modules (<script type="module">). See bug 40854862.Samsung Internet: Not supported for ECMAScript Modules (<script type="module">). See bug 40854862.WebView Android: Not supported for ECMAScript Modules (<script type="module">). See bug 40854862.
http.headers.Strict-Transport-Security 📋Chrome1/25/2010 Firefox3/22/2011421
http.headers.TE 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Timing-Allow-Origin 📋Firefox3/8/2016 Chrome10/12/2016218
http.headers.Transfer-Encoding 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Upgrade 📋Chrome5/25/2010 Firefox8/16/2011448
http.headers.Upgrade-Insecure-Requests 📋Chrome7/21/2015 Firefox8/2/2016378
http.headers.User-Agent 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Vary 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Via 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.WWW-Authenticate 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.WWW-Authenticate.Basic 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.WWW-Authenticate.Digest 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.WWW-Authenticate.Digest.SHA-256 Firefox10/5/2021 Chrome9/12/2023707
http.headers.WWW-Authenticate.Digest.md5 Firefox11/9/2004 Chrome12/11/20081493
http.headers.WWW-Authenticate.NTLM Firefox11/9/2004 Chrome12/11/20081493
http.headers.WWW-Authenticate.Negotiate 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.Warning 📋Firefox11/9/2004 Chrome12/11/20081493
http.headers.X-Content-Type-Options 📋Firefox11/15/2016 Chrome1/23/2018434
Chrome: Not supported for stylesheets.Chrome Android: Not supported for stylesheets.Opera: Not supported for stylesheets.Opera Android: Not supported for stylesheets.Samsung Internet: Not supported for stylesheets.WebView Android: Not supported for stylesheets.
http.headers.X-DNS-Prefetch-Control Firefox10/24/2006 Chrome12/11/2008779
http.headers.X-Frame-Options 📋Chrome1/25/2010 Firefox3/22/2011421
http.headers.X-Frame-Options.SAMEORIGIN Chrome1/25/2010 Firefox3/22/2011421
Chrome: Starting in Chrome 61, this applies to all of a frame's ancestors.Chrome Android: Starting in Chrome Android 61, this applies to all of a frame's ancestors.Firefox: Starting in Firefox 59, this applies to all of a frame's ancestors.Firefox for Android: Starting in Firefox for Android 59, this applies to all of a frame's ancestors.Quest Browser: Starting in Quest Browser 5.0, this applies to all of a frame's ancestors.Opera: Starting in Opera 48, this applies to all of a frame's ancestors.Opera Android: Starting in Opera Android 45, this applies to all of a frame's ancestors.Samsung Internet: Starting in Samsung Internet 8.0, this applies to all of a frame's ancestors.WebView Android: Starting in WebView Android 61, this applies to all of a frame's ancestors.
http.methods.CONNECT 📋Firefox11/9/2004 Chrome12/11/20081493
http.methods.DELETE 📋Firefox11/9/2004 Chrome12/11/20081493
http.methods.GET 📋Firefox11/9/2004 Chrome12/11/20081493
http.methods.HEAD 📋Firefox11/9/2004 Chrome12/11/20081493
http.methods.OPTIONS 📋Firefox11/9/2004 Chrome12/11/20081493
http.methods.POST 📋Firefox11/9/2004 Chrome12/11/20081493
http.methods.PUT 📋Firefox11/9/2004 Chrome12/11/20081493
http.mixed-content 📋Firefox8/6/2013 Chrome12/10/20192317
http.mixed-content.allow_file_urls 📋Firefox8/6/2013 Chrome12/10/20192317
http.mixed-content.allow_localhost_url 📋Chrome12/10/2019 Firefox12/15/2020371
http.mixed-content.allow_loopback_url 📋Firefox8/8/2017 Chrome12/10/2019854
http.mixed-content.auto_upgrade_images 📋Chrome10/20/2020 Firefox6/11/20241330
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 📋Chrome2/4/2020 Firefox6/11/20241589
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 📋Firefox7/13/2021 Chrome7/20/20217
http.mixed-content.blockable_mixed_content 📋Firefox8/6/2013 Chrome12/10/20192317
Chrome: From version 79 blocks iframes, scripts, and stylesheets.Chrome Android: From version 79 blocks iframes, scripts, and stylesheets.Edge: From version 79 blocks iframes, scripts, and stylesheets.Quest Browser: From version 8.0 blocks iframes, scripts, and stylesheets.Opera: From version 66 blocks iframes, scripts, and stylesheets.Opera Android: From version 57 blocks iframes, scripts, and stylesheets.Samsung Internet: From version 12.0 blocks iframes, scripts, and stylesheets.WebView Android: From version 79 blocks iframes, scripts, and stylesheets.
http.status.103 📋Chrome6/21/2022 Firefox11/21/2023518
Chrome: Supported in HTTP/2 and later only.Chrome Android: Supported in HTTP/2 and later only.Edge: Supported in HTTP/2 and later only.Quest Browser: Supported in HTTP/2 and later only.Opera: Supported in HTTP/2 and later only.Opera Android: Supported in HTTP/2 and later only.Safari: Supported in HTTP/2 and later only.Safari on iOS: Supported in HTTP/2 and later only.Samsung Internet: Supported in HTTP/2 and later only.WebView Android: Supported in HTTP/2 and later only.WebView on iOS: Supported in HTTP/2 and later only.
http.status.103.preconnect Chrome6/21/2022 Firefox11/21/2023518
http.status.103.preload Chrome6/21/2022 Firefox2/20/2024609
http.status.308 📋Firefox7/17/2012 Chrome7/16/2014729
Internet Explorer: Does not work below Windows 10.