Experimental

For a given set of browsers what APIs are still considred experimental, and how long have they been experimental?

Example Comparisons
Browsers
Features

Summary

Experimental APIs

Below is a list of features that are marked as "Experimental" in Firefox and Safari

Raw Data

Quick Links:

DOM API Data

API First Browser Date Last Browser Date Days in experimentation Notes
api.Animation.commitStyles.endpoint_inclusive_commitStyles 📋Firefox8/19/2025 326
api.AudioSession 📋Safari3/27/2023 1202
api.AudioSession.type 📋Safari3/27/2023 1202
api.AudioWorklet.port 📋Firefox4/29/2025 438
api.AudioWorkletGlobalScope.port 📋Firefox4/29/2025 438
api.BarcodeDetector 📋Safari9/18/2023 1027
Chrome: Supported on ChromeOS and macOS only.Chrome: Before Chrome 113, on macOS Ventura (13) and above, this interface silently failed. See bug 40245611.Chrome: Supported on macOS only.Edge: Supported on macOS only.Edge: Before Chrome 113, on macOS Ventura (13) and above, this interface silently failed. See bug 40245611.Opera: Supported on macOS only.Opera: Before Chrome 113, on macOS Ventura (13) and above, this interface silently failed. See bug 40245611.
api.BarcodeDetector.BarcodeDetector 📋Safari9/18/2023 1027
Chrome: Supported on ChromeOS and macOS only.Chrome: Supported on macOS only.Edge: Supported on macOS only.Opera: Supported on macOS only.
api.BarcodeDetector.detect 📋Safari9/18/2023 1027
Chrome: Supported on ChromeOS and macOS only.Chrome: Supported on macOS only.Edge: Supported on macOS only.Opera: Supported on macOS only.
api.BarcodeDetector.getSupportedFormats_static 📋Safari9/18/2023 1027
Chrome: Supported on ChromeOS and macOS only.Chrome: Supported on macOS only.Edge: Supported on macOS only.Opera: Supported on macOS only.
api.BufferedChangeEvent 📋Safari9/18/2023 1027
api.BufferedChangeEvent.BufferedChangeEvent 📋Safari9/18/2023 1027
api.BufferedChangeEvent.addedRanges 📋Safari9/18/2023 1027
api.BufferedChangeEvent.removedRanges 📋Safari9/18/2023 1027
api.CSSCustomMediaRule 📋Firefox12/9/2025 214
api.CSSFontFaceDescriptors 📋Safari9/15/2025 299
api.CSSFontFaceDescriptors.font-display 📋Safari9/15/2025 299
api.CSSFontFaceDescriptors.font-family 📋Safari9/15/2025 299
api.CSSFontFaceDescriptors.font-feature-settings 📋Safari9/15/2025 299
api.CSSFontFaceDescriptors.font-stretch 📋Safari9/15/2025 299
api.CSSFontFaceDescriptors.font-style 📋Safari9/15/2025 299
api.CSSFontFaceDescriptors.font-weight 📋Safari9/15/2025 299
api.CSSFontFaceDescriptors.font-width 📋Safari9/15/2025 299
api.CSSFontFaceDescriptors.fontDisplay 📋Safari9/15/2025 299
api.CSSFontFaceDescriptors.fontFamily 📋Safari9/15/2025 299
api.CSSFontFaceDescriptors.fontFeatureSettings 📋Safari9/15/2025 299
api.CSSFontFaceDescriptors.fontStretch 📋Safari9/15/2025 299
api.CSSFontFaceDescriptors.fontStyle 📋Safari9/15/2025 299
api.CSSFontFaceDescriptors.fontWeight 📋Safari9/15/2025 299
api.CSSFontFaceDescriptors.fontWidth 📋Safari9/15/2025 299
api.CSSFontFaceDescriptors.size-adjust 📋Safari9/15/2025 299
api.CSSFontFaceDescriptors.sizeAdjust 📋Safari9/15/2025 299
api.CSSFontFaceDescriptors.src 📋Safari9/15/2025 299
api.CSSFontFaceDescriptors.unicode-range 📋Safari9/15/2025 299
api.CSSFontFaceDescriptors.unicodeRange 📋Safari9/15/2025 299
api.CSSPageDescriptors.page-orientation 📋Firefox8/6/2024 704
api.CSSPageDescriptors.pageOrientation 📋Firefox8/6/2024 704
api.CSSPseudoElement 📋Firefox4/7/2020 2286
api.CSSPseudoElement.element 📋Firefox4/7/2020 2286
api.CSSPseudoElement.type 📋Firefox4/7/2020 2286
api.CompressionStream.CompressionStream.zstd Firefox4/29/2025 438
api.Credential.isConditionalMediationAvailable_static 📋Safari9/12/2022 1398
api.DataCue 📋Safari9/19/2017 3217
api.DataCue.DataCue 📋Safari9/19/2017 3217
api.DataCue.type 📋Safari9/19/2017 3217
api.DataCue.value 📋Safari9/19/2017 3217
api.DataTransfer.addElement Firefox6/30/2009 6220
api.DataTransfer.mozCursor Firefox6/30/2009 6220
api.DataTransfer.mozSourceNode Firefox3/22/2011 5590
api.DataTransfer.mozUserCancelled Firefox6/30/2009 6220
api.DecompressionStream.DecompressionStream.zstd Firefox4/29/2025 438
api.DeprecationReportBody 📋Firefox1/29/2019 2720
Firefox: Not supported in workers
api.DeprecationReportBody.anticipatedRemoval 📋Firefox1/29/2019 2720
api.DeprecationReportBody.columnNumber 📋Firefox1/29/2019 2720
api.DeprecationReportBody.id 📋Firefox1/29/2019 2720
api.DeprecationReportBody.lineNumber 📋Firefox1/29/2019 2720
api.DeprecationReportBody.message 📋Firefox1/29/2019 2720
api.DeprecationReportBody.sourceFile 📋Firefox1/29/2019 2720
api.Directory Firefox6/10/2014 4414
api.Directory.getFiles Firefox8/2/2016 3630
api.Directory.getFilesAndDirectories Firefox11/3/2015 3903
api.Directory.name Firefox6/10/2014 4414
api.Directory.path Firefox11/3/2015 3903
api.Document.featurePolicy Firefox9/3/2019 2503
api.Document.getBoxQuads 📋Firefox7/22/2014 4372
api.Document.parseHTML_static 📋Firefox2/24/2026 137
api.Element.animate.options_iterationComposite_parameter 📋Firefox8/25/2020 2146
api.Element.getBoxQuads 📋Firefox7/22/2014 4372
api.FeaturePolicy Firefox1/29/2019 2720
api.FeaturePolicy.allowedFeatures Firefox1/29/2019 2720
api.FeaturePolicy.allowsFeature Firefox1/29/2019 2720
api.FeaturePolicy.features Firefox10/22/2019 2454
api.FeaturePolicy.getAllowlistForFeature Firefox1/29/2019 2720
api.FetchEvent.respondWith.resource_url Firefox3/13/2018 3042
api.Gamepad.hand 📋Firefox8/8/2017 3259
api.Gamepad.hapticActuators 📋Firefox8/8/2017 3259
api.Gamepad.pose 📋Firefox8/8/2017 3259
api.Gamepad.secure_context_required Firefox8/10/2021 1796
api.GamepadButton.secure_context_required Firefox8/10/2021 1796
api.GamepadEvent.secure_context_required Firefox8/10/2021 1796
api.GamepadPose 📋Firefox8/8/2017 3259
api.GamepadPose.angularAcceleration 📋Firefox8/8/2017 3259
api.GamepadPose.angularVelocity 📋Firefox8/8/2017 3259
api.GamepadPose.hasOrientation 📋Firefox8/8/2017 3259
api.GamepadPose.hasPosition 📋Firefox8/8/2017 3259
api.GamepadPose.linearAcceleration 📋Firefox8/8/2017 3259
api.GamepadPose.linearVelocity 📋Firefox8/8/2017 3259
api.GamepadPose.orientation 📋Firefox8/8/2017 3259
api.GamepadPose.position 📋Firefox8/8/2017 3259
api.GamepadPose.secure_context_required Firefox8/10/2021 1796
api.HTMLAnchorElement.attributionSourceId 📋Safari3/14/2022 1580
api.HTMLIFrameElement.featurePolicy Firefox9/3/2019 2503
api.HTMLInputElement.alpha 📋Safari3/31/2025 467
api.HTMLInputElement.colorSpace 📋Safari3/31/2025 467
api.HTMLOutputElement.HTMLOutputElement 📋Safari9/20/2021 1755
api.IDBDatabase.transaction.mode_parameter_readwriteflush Firefox8/11/2015 3987
api.InputEvent.inputType.insertFromPasteAsQuotation Firefox5/21/2019 2608
api.IntersectionObserverEntry.IntersectionObserverEntry 📋Safari3/25/2019 2665
api.ManagedMediaSource 📋Safari9/18/2023 1027
api.ManagedMediaSource.ManagedMediaSource 📋Safari9/18/2023 1027
api.ManagedMediaSource.endstreaming_event 📋Safari9/18/2023 1027
api.ManagedMediaSource.startstreaming_event 📋Safari9/18/2023 1027
api.ManagedMediaSource.streaming 📋Safari9/18/2023 1027
api.ManagedSourceBuffer 📋Safari9/18/2023 1027
api.ManagedSourceBuffer.bufferedchange_event 📋Safari9/18/2023 1027
api.MediaDevices.selectAudioOutput 📋Firefox8/1/2023 1075
api.MediaSession.setScreenshareActive 📋Safari3/31/2025 467
api.Navigator.audioSession 📋Safari3/27/2023 1202
api.Navigator.getAutoplayPolicy 📋Firefox4/11/2023 1187
api.Navigator.getGamepads.secure_context_required Firefox8/10/2021 1796
api.Navigator.globalPrivacyControl 📋Firefox11/21/2023 963
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.
api.Navigator.registerProtocolHandler.scheme_parameter_ftp Firefox3/8/2022 1586
api.Navigator.registerProtocolHandler.scheme_parameter_ftps Firefox3/8/2022 1586
api.Navigator.registerProtocolHandler.scheme_parameter_sftp Firefox3/8/2022 1586
api.Notification.navigate 📋Safari3/31/2025 467
api.PerformanceResourceTiming.contentType 📋Firefox8/6/2024 704
api.PushEvent.notification 📋Safari3/31/2025 467
Safari on iOS: Notifications are supported in web apps saved to the home screen.
api.RTCDataChannel.priority 📋Safari9/20/2021 1755
api.RTCIdentityAssertion 📋Firefox8/11/2015 3987
Firefox: The RTCIdentityAssertion interface itself is not present, but an object with the same properties is usedFirefox for Android: The RTCIdentityAssertion interface itself is not present, but an object with the same properties is used
api.RTCIdentityAssertion.idp 📋Firefox8/11/2015 3987
api.RTCIdentityAssertion.name 📋Firefox8/11/2015 3987
api.RTCStatsReport.type_inbound-rtp.estimatedPlayoutTimestamp 📋Firefox8/19/2025 326
api.RTCStatsReport.type_inbound-rtp.framesAssembledFromMultiplePackets 📋Firefox8/19/2025 326
api.RTCStatsReport.type_inbound-rtp.freezeCount 📋Firefox8/19/2025 326
api.RTCStatsReport.type_inbound-rtp.pauseCount 📋Firefox8/19/2025 326
api.RTCStatsReport.type_inbound-rtp.totalAssemblyTime 📋Firefox8/19/2025 326
api.RTCStatsReport.type_inbound-rtp.totalFreezesDuration 📋Firefox8/19/2025 326
api.RTCStatsReport.type_inbound-rtp.totalPausesDuration 📋Firefox8/19/2025 326
api.RTCStatsReport.type_outbound-rtp.totalEncodedBytesTarget 📋Firefox6/28/2022 1474
api.RTCStatsReport.type_remote-inbound-rtp.packetsReceived 📋Firefox1/7/2020 2377
api.ReadableStream.from_static 📋Firefox8/29/2023 1047
api.ReportingObserver.worker_support Firefox6/2/2020 2230
api.Request.destination.speculationrules Safari12/12/2025 211
api.SVGPathElement.getPathData 📋Firefox4/1/2025 466
api.SVGPathElement.getPathSegmentAtLength 📋Firefox4/1/2025 466
api.SVGPathElement.setPathData 📋Firefox4/1/2025 466
api.SVGScriptElement.defer Firefox8/29/2023 1047
api.ShadowRoot.referenceTarget Safari9/15/2025 Firefox3/24/2026190
api.ShadowRoot.setHTML 📋Firefox2/24/2026 137
api.SourceBuffer.appendBufferAsync Firefox9/5/2018 2866
api.SourceBuffer.removeAsync Firefox9/5/2018 2866
api.SourceBuffer.textTracks 📋Safari10/16/2014 4286
Safari on iOS: Exposed in Mobile Safari on iPad but not on iPhone.
api.Text.getBoxQuads 📋Firefox7/22/2014 4372
api.VideoTrackGenerator 📋Safari9/16/2024 663
api.VideoTrackGenerator.VideoTrackGenerator 📋Safari9/16/2024 663
api.VideoTrackGenerator.muted 📋Safari9/16/2024 663
api.VideoTrackGenerator.track 📋Safari9/16/2024 663
api.VideoTrackGenerator.writable 📋Safari9/16/2024 663
api.WebGLActiveInfo.worker_support Firefox9/20/2022 1390
api.WebGLBuffer.worker_support Firefox9/20/2022 1390
api.WebGLContextEvent.worker_support Firefox9/20/2022 1390
api.WebGLFramebuffer.worker_support Firefox9/20/2022 1390
api.WebGLProgram.worker_support Firefox9/20/2022 1390
api.WebGLRenderbuffer.worker_support Firefox9/20/2022 1390
api.WebGLRenderingContext.worker_support Firefox9/20/2022 1390
api.WebGLShader.worker_support Firefox9/20/2022 1390
api.WebGLShaderPrecisionFormat.worker_support Firefox9/20/2022 1390
api.WebGLTexture.worker_support Firefox9/20/2022 1390
api.WebGLUniformLocation.worker_support Firefox9/20/2022 1390
api.Window.pushManager 📋Safari3/31/2025 467
Safari on iOS: Notifications are supported in web apps saved to the home screen.
api.WindowClient.ancestorOrigins 📋Safari9/12/2022 1398
api.WorkerNavigator.globalPrivacyControl 📋Firefox11/21/2023 963
Firefox: Opt-in to GPC 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.

CSS Data

API First Browser Date Last Browser Date Days in experimentation Notes
css.at-rules.custom-media 📋Firefox2/24/2026 137
css.at-rules.font-face.font-width 📋Safari3/31/2025 467
css.at-rules.media.prefers-reduced-transparency 📋Firefox5/9/2023 1159
css.properties.-webkit-column-axis Safari7/25/2012 5099
css.properties.-webkit-column-progression Safari10/22/2013 4645
css.properties.-webkit-cursor-visibility Safari10/22/2013 4645
css.properties.-webkit-hyphenate-limit-after Safari7/20/2011 5470
css.properties.-webkit-hyphenate-limit-before Safari7/20/2011 5470
css.properties.-webkit-hyphenate-limit-lines Safari7/25/2012 5099
css.properties.-webkit-line-align Safari7/25/2012 5099
css.properties.-webkit-line-box-contain Safari7/20/2011 5470
css.properties.-webkit-line-grid Safari7/25/2012 5099
css.properties.-webkit-line-snap Safari7/25/2012 5099
css.properties.-webkit-mask-source-type Safari10/22/2013 4645
css.properties.-webkit-nbsp-mode Safari6/8/2009 6242
css.properties.-webkit-text-zoom Safari9/20/2016 3581
css.properties.background.x-end 📋Safari9/15/2025 299
css.properties.background.x-start 📋Safari9/15/2025 299
css.properties.background.y-end 📋Safari9/15/2025 299
css.properties.background.y-start 📋Safari9/15/2025 299
css.properties.background-image.element 📋Firefox3/22/2011 5590
css.properties.background-position.x-end 📋Safari9/15/2025 299
css.properties.background-position.x-start 📋Safari9/15/2025 299
css.properties.background-position.y-end 📋Safari9/15/2025 299
css.properties.background-position.y-start 📋Safari9/15/2025 299
css.properties.background-position-x.x-end 📋Safari9/15/2025 299
css.properties.background-position-x.x-start 📋Safari9/15/2025 299
css.properties.background-position-y.y-end 📋Safari9/15/2025 299
css.properties.background-position-y.y-start 📋Safari9/15/2025 299
css.properties.block-size.fit-content_function Firefox8/10/2021 1796
css.properties.break-after.always Firefox1/29/2019 2720
css.properties.break-before.always Firefox1/29/2019 2720
css.properties.content.none_applies_to_elements Firefox8/10/2021 1796
css.properties.counter-reset.reset_does_not_affect_siblings Firefox10/20/2020 2090
css.properties.counter-reset.reversed 📋Firefox1/11/2022 1642
css.properties.font-synthesis-position 📋Firefox9/26/2023 1019
css.properties.font-synthesis-position.auto 📋Firefox9/26/2023 1019
css.properties.font-synthesis-position.none 📋Firefox9/26/2023 1019
css.properties.font-synthesis-style.oblique-only 📋Firefox4/1/2025 466
css.properties.font-width 📋Safari3/31/2025 467
css.properties.font-width.condensed 📋Safari3/31/2025 467
css.properties.font-width.expanded 📋Safari3/31/2025 467
css.properties.font-width.extra-condensed 📋Safari3/31/2025 467
css.properties.font-width.extra-expanded 📋Safari3/31/2025 467
css.properties.font-width.normal 📋Safari3/31/2025 467
css.properties.font-width.percentage 📋Safari3/31/2025 467
css.properties.font-width.semi-condensed 📋Safari3/31/2025 467
css.properties.font-width.semi-expanded 📋Safari3/31/2025 467
css.properties.font-width.ultra-condensed 📋Safari3/31/2025 467
css.properties.font-width.ultra-expanded 📋Safari3/31/2025 467
css.properties.grid-template-columns.masonry 📋Firefox6/2/2020 2230
css.properties.grid-template-rows.masonry 📋Firefox6/2/2020 2230
css.properties.height.fit-content_function 📋Firefox8/10/2021 1796
css.properties.image-rendering.smooth 📋Firefox10/5/2021 1740
css.properties.inline-size.fit-content_function Firefox8/10/2021 1796
css.properties.margin-trim 📋Safari3/27/2023 1202
css.properties.margin-trim.block 📋Safari3/27/2023 1202
css.properties.margin-trim.block-end 📋Safari3/27/2023 1202
css.properties.margin-trim.block-start 📋Safari3/27/2023 1202
css.properties.margin-trim.inline 📋Safari3/27/2023 1202
css.properties.margin-trim.inline-end 📋Safari3/27/2023 1202
css.properties.margin-trim.inline-start 📋Safari3/27/2023 1202
css.properties.margin-trim.none 📋Safari3/27/2023 1202
css.properties.mask.x-end 📋Safari9/15/2025 299
css.properties.mask.x-start 📋Safari9/15/2025 299
css.properties.mask.y-end 📋Safari9/15/2025 299
css.properties.mask.y-start 📋Safari9/15/2025 299
css.properties.mask-position.x-end 📋Safari9/15/2025 299
css.properties.mask-position.x-start 📋Safari9/15/2025 299
css.properties.mask-position.y-end 📋Safari9/15/2025 299
css.properties.mask-position.y-start 📋Safari9/15/2025 299
css.properties.max-block-size.fit-content_function Firefox8/10/2021 1796
css.properties.max-height.fit-content_function 📋Firefox8/10/2021 1796
css.properties.max-inline-size.fit-content_function Firefox8/10/2021 1796
css.properties.max-width.fit-content_function 📋Firefox8/10/2021 1796
css.properties.min-block-size.fit-content_function Firefox8/10/2021 1796
css.properties.min-height.fit-content_function 📋Firefox8/10/2021 1796
css.properties.min-inline-size.fit-content_function Firefox8/10/2021 1796
css.properties.min-width.fit-content_function 📋Firefox8/10/2021 1796
css.properties.mix-blend-mode.plus-darker 📋Safari9/30/2015 3937
css.properties.object-position.x-end 📋Safari9/15/2025 299
css.properties.object-position.x-start 📋Safari9/15/2025 299
css.properties.object-position.y-end 📋Safari9/15/2025 299
css.properties.object-position.y-start 📋Safari9/15/2025 299
css.properties.offset.margin-box 📋Safari9/12/2022 1398
css.properties.offset.x-end 📋Safari9/15/2025 299
css.properties.offset.x-start 📋Safari9/15/2025 299
css.properties.offset.y-end 📋Safari9/15/2025 299
css.properties.offset.y-start 📋Safari9/15/2025 299
css.properties.offset-anchor.x-end 📋Safari9/15/2025 299
css.properties.offset-anchor.x-start 📋Safari9/15/2025 299
css.properties.offset-anchor.y-end 📋Safari9/15/2025 299
css.properties.offset-anchor.y-start 📋Safari9/15/2025 299
css.properties.offset-path.margin-box 📋Safari9/16/2024 663
css.properties.offset-position.x-end 📋Safari9/15/2025 299
css.properties.offset-position.x-start 📋Safari9/15/2025 299
css.properties.offset-position.y-end 📋Safari9/15/2025 299
css.properties.offset-position.y-start 📋Safari9/15/2025 299
css.properties.perspective-origin.x-end 📋Safari9/15/2025 299
css.properties.perspective-origin.x-start 📋Safari9/15/2025 299
css.properties.perspective-origin.y-end 📋Safari9/15/2025 299
css.properties.perspective-origin.y-start 📋Safari9/15/2025 299
css.properties.ruby-position.alternate Firefox4/19/2021 1909
css.properties.speak-as 📋Safari4/12/2018 3012
css.properties.speak-as.digits 📋Safari4/12/2018 3012
css.properties.speak-as.literal-punctuation 📋Safari4/12/2018 3012
css.properties.speak-as.no-punctuation 📋Safari4/12/2018 3012
css.properties.speak-as.normal 📋Safari4/12/2018 3012
css.properties.speak-as.spell-out 📋Safari4/12/2018 3012
css.properties.stroke-color 📋Safari4/12/2018 3012
css.properties.stroke-color.currentColor 📋Safari4/12/2018 3012
css.properties.stroke-color.transparent 📋Safari4/12/2018 3012
css.properties.text-align-last.match-parent 📋Safari9/12/2022 1398
css.properties.text-autospace.insert 📋Firefox11/11/2025 242
css.properties.text-box.cap 📋Safari12/11/2024 577
css.properties.text-box.ex 📋Safari12/11/2024 577
css.properties.text-box.ideographic 📋Safari12/11/2024 577
css.properties.text-box.ideographic-ink 📋Safari12/11/2024 577
css.properties.text-box-edge.cap 📋Safari12/11/2024 577
css.properties.text-box-edge.ex 📋Safari12/11/2024 577
css.properties.text-box-edge.ideographic 📋Safari12/11/2024 577
css.properties.text-box-edge.ideographic-ink 📋Safari12/11/2024 577
css.properties.text-decoration-inset 📋Firefox12/9/2025 214
css.properties.text-decoration-inset.auto 📋Firefox12/9/2025 214
css.properties.text-decoration-skip 📋Safari3/25/2019 2665
Chrome: Only supported the deprecated ink value.Chrome Android: Only supported the deprecated ink value.Opera: Only supported the deprecated ink value.Opera Android: Only supported the deprecated ink value.Samsung Internet: Only supported the deprecated ink value.WebView Android: Only supported the deprecated ink value.
css.properties.text-decoration-skip.auto 📋Safari10/22/2013 4645
css.properties.text-decoration-skip.none 📋Safari10/22/2013 4645
css.properties.text-emphasis-position.auto Firefox10/29/2024 620
css.properties.white-space.preserve-spaces 📋Firefox3/19/2024 844
css.properties.white-space-collapse.preserve-spaces 📋Firefox3/19/2024 844
css.properties.width.fit-content_function 📋Firefox8/10/2021 1796
css.selectors.-moz-first-node Firefox8/8/2017 3259
css.selectors.-moz-last-node Firefox8/8/2017 3259
css.selectors.-moz-list-bullet Firefox11/9/2004 7914
css.selectors.-moz-list-number Firefox11/9/2004 7914
css.selectors.-moz-progress-bar Firefox8/16/2011 5443
css.selectors.marker.counter_support 📋Firefox1/13/2026 179
css.selectors.marker.quotes_support 📋Firefox1/13/2026 179
css.types.image.element 📋Firefox11/14/2017 3161
Firefox: -moz-element() is limited to background-image, background, border-image and border-image-source.Firefox: -moz-element() is limited to background-image and background.Firefox for Android: -moz-element() is limited to background-image, background, border-image and border-image-source.Firefox for Android: -moz-element() is limited to background-image and background.
css.types.random 📋Safari12/12/2025 211
css.types.random.dashed-ident 📋Safari12/12/2025 211
css.types.random.element-shared 📋Safari12/12/2025 211
css.types.random.step 📋Safari12/12/2025 211
css.types.ratio.number_value Firefox6/30/2020 2202

HTML Data

API First Browser Date Last Browser Date Days in experimentation Notes
html.elements.a.attributionsourceid 📋Safari4/26/2021 1902
html.elements.iframe.allow.document-domain 📋Firefox3/10/2020 2314
html.elements.iframe.allow.gamepad 📋Firefox8/10/2021 1796
Firefox: The default allowlist is * instead of self (as required by the specification).Firefox for Android: The default allowlist is * instead of self (as required by the specification).
html.elements.iframe.allow.speaker-selection 📋Firefox8/1/2023 1075
Firefox for Android: Not available due to a limitation in Android (see bug 1473346).
html.elements.input.alpha 📋Safari3/31/2025 467
html.elements.input.colorspace 📋Safari3/31/2025 467
html.elements.input.switch Safari3/5/2024 858
html.elements.script.type.speculationrules 📋Safari12/12/2025 211
Chrome: Initial support included same-origin prerendering only.Chrome Android: Initial support included same-origin prerendering only.Edge: Initial support included same-origin prerendering only.Quest Browser: Initial support included same-origin prerendering only.Opera: Initial support included same-origin prerendering only.Opera Android: Initial support included same-origin prerendering only.Samsung Internet: Initial support included same-origin prerendering only.WebView Android: Initial support included same-origin prerendering only.
html.elements.script.type.speculationrules.eagerness 📋Safari12/12/2025 211
Safari: Only conservative is supported for document rules (though moderate automatically falls back to conservative). Only eager and immediate is supported for list rules.Safari on iOS: Only conservative is supported for document rules (though moderate automatically falls back to conservative). Only eager and immediate is supported for list rules.
html.elements.script.type.speculationrules.prefetch 📋Safari12/12/2025 211
html.elements.script.type.speculationrules.referrer_policy 📋Safari12/12/2025 211
html.elements.script.type.speculationrules.relative_to 📋Safari12/12/2025 211
html.elements.script.type.speculationrules.source_optional 📋Safari12/12/2025 211
html.elements.script.type.speculationrules.tag 📋Safari12/12/2025 211
html.elements.script.type.speculationrules.urls 📋Safari12/12/2025 211
html.elements.script.type.speculationrules.where 📋Safari12/12/2025 211
html.elements.template.shadowrootreferencetarget Safari9/15/2025 Firefox3/24/2026190

JS Data

API First Browser Date Last Browser Date Days in experimentation Notes
javascript.builtins.Intl.PluralRules.PluralRules.options_parameter.options_trailingZeroDisplay_parameter Firefox8/1/2023 1075
javascript.builtins.Iterator.zip 📋Firefox2/24/2026 137
javascript.builtins.Iterator.zipKeyed 📋Firefox2/24/2026 137
javascript.builtins.Temporal.Instant.Instant 📋Firefox5/27/2025 410
javascript.builtins.Temporal.PlainDate.PlainDate 📋Firefox5/27/2025 410
javascript.builtins.Temporal.PlainDateTime.PlainDateTime 📋Firefox5/27/2025 410
javascript.builtins.Temporal.PlainMonthDay.PlainMonthDay 📋Firefox5/27/2025 410
javascript.builtins.Temporal.PlainYearMonth.PlainYearMonth 📋Firefox5/27/2025 410
javascript.builtins.Temporal.ZonedDateTime.ZonedDateTime 📋Firefox5/27/2025 410