Discouraged features

Using the following features is discouraged, even if they're still implemented in browsers, because standards bodies and/or browser implementers have agreed that they should not be used.

• Accessor methods

  The __defineGetter__() and __defineSetter__() methods of objects bind a function to a property, which is called on setting or reading the property.

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  • Chrome 1 Released on 2008-12-11
  • Chrome Android 18 Released on 2012-06-27
  • Edge 12 Released on 2015-07-29
  • Firefox 1 Released on 2004-11-09
  • Firefox for Android 4 Released on 2011-03-29
  • Safari 3 Released on 2007-10-26
  • Safari on iOS 1 Released on 2007-06-29

• Ad selection

  The Ad Selection API facilitates advertisement sales by allowing sites to register users as part of an interest group or to choose which ads appear based on those interest groups, while minimizing the ability of advertisers to track specific members of the interest group.

  Learn more

  • Chrome Not supported
  • Chrome Android Not supported
  • Edge Not supported
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari Not supported
  • Safari on iOS Not supported

• arguments.callee

  The callee property of the arguments variable in a non-strict function body's local scope is the function that arguments belongs to.

  Learn more

  • Chrome 1 Released on 2008-12-11
  • Chrome Android 18 Released on 2012-06-27
  • Edge 12 Released on 2015-07-29
  • Firefox 1 Released on 2004-11-09
  • Firefox for Android 4 Released on 2011-03-29
  • Safari 1 Released on 2003-06-23
  • Safari on iOS 1 Released on 2007-06-29

• Attribution reporting

  The attribution reporting API measures when an ad click or view leads to a conversion, such as a purchase on an advertiser site.

  Learn more

  • Chrome 133 Released on 2025-02-04
  • Chrome Android 133 Released on 2025-02-04
  • Edge 133 Released on 2025-02-06
  • Firefox Not supported Position
  • Firefox for Android Not supported Position
  • Safari Not supported Position
  • Safari on iOS Not supported Position

• AudioListener setPosition() and setOrientation()

  The setPosition() and setOrientation() methods of the AudioListener API set the virtual position and orientation of a person relative to sound sources, to spatialize audio in a Web Audio context.

  Learn more

  • Chrome 14 Released on 2011-09-16
  • Chrome Android 18 Released on 2012-06-27
  • Edge 12 Released on 2015-07-29
  • Firefox 25 Released on 2013-10-29
  • Firefox for Android 25 Released on 2013-10-29
  • Safari 6 Released on 2012-07-25
  • Safari on iOS 6 Released on 2012-09-10

• clip

  The clip CSS property sets the visible area of an absolutely positioned element.

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  • Chrome 1 Released on 2008-12-11
  • Chrome Android 18 Released on 2012-06-27
  • Edge 79 Released on 2020-01-15
  • Firefox 1 Released on 2004-11-09
  • Firefox for Android 4 Released on 2011-03-29
  • Safari 1.3 Released on 2005-04-15
  • Safari on iOS 1 Released on 2007-06-29

• color-adjust

  The color-adjust shorthand CSS property allows multiple performance related color adjustments to be set at once. Setting the print-color-adjust CSS property directly is preferred, as it is the only such adjustment so far defined.

  Learn more

  • Chrome Not supported
  • Chrome Android Not supported
  • Edge Not supported
  • Firefox 48 Released on 2016-08-02
  • Firefox for Android 48 Released on 2016-08-02
  • Safari 15.4 Released on 2022-03-14
  • Safari on iOS 15.4 Released on 2022-03-14

  Baseline availability blocked since March 2022 by Chromium (52 months)

• color-contrast()

  The color-contrast() CSS function picks a color from a list that has the most contrast with another color.

  Learn more

  • Chrome Not supported
  • Chrome Android Not supported
  • Edge Not supported
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari Not supported
  • Safari on iOS Not supported

• CSS object model (DOM level 2)

  The DOM level 2 style specification defined interfaces to access and modify CSS styles, such as CSSValue and CSSPrimitiveValue, that were later excluded from the CSS object model.

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  • Chrome Not supported
  • Chrome Android Not supported
  • Edge Not supported
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari 10 Released on 2016-09-20
  • Safari on iOS 10 Released on 2016-09-13

• getYear() and setYear()

  The getYear() and setYear() methods of Date objects get and set the year as an offset to 1900.

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  • Chrome 1 Released on 2008-12-11
  • Chrome Android 18 Released on 2012-06-27
  • Edge 12 Released on 2015-07-29
  • Firefox 1 Released on 2004-11-09
  • Firefox for Android 4 Released on 2011-03-29
  • Safari 1 Released on 2003-06-23
  • Safari on iOS 1 Released on 2007-06-29

• toGMTString()

  The toGMTString() method of Date objects is an alias to the toUTCString() method.

  Learn more

  • Chrome 1 Released on 2008-12-11
  • Chrome Android 18 Released on 2012-06-27
  • Edge 12 Released on 2015-07-29
  • Firefox 1 Released on 2004-11-09
  • Firefox for Android 4 Released on 2011-03-29
  • Safari 1 Released on 2003-06-23
  • Safari on iOS 1 Released on 2007-06-29

• Device media queries

  The device-aspect-ratio, device-height, and device-width media features describe physical properties of the displaying output device.

  Learn more

  • Chrome 1 Released on 2008-12-11
  • Chrome Android 18 Released on 2012-06-27
  • Edge 12 Released on 2015-07-29
  • Firefox 2 Released on 2006-10-24
  • Firefox for Android 4 Released on 2011-03-29
  • Safari 3 Released on 2007-10-26
  • Safari on iOS 1 Released on 2007-06-29

• Document colors

  A document's bgColor, fgColor, alinkColor, linkColor, and vlinkColor properties get and set the background, foreground, active link, link, and visited link colors of that document.

  Learn more

  • Chrome 64 Released on 2018-01-23
  • Chrome Android 64 Released on 2018-01-23
  • Edge 12 Released on 2015-07-29
  • Firefox 69 Released on 2019-09-03
  • Firefox for Android 79 Released on 2020-07-28
  • Safari 11 Released on 2017-09-19
  • Safari on iOS 11 Released on 2017-09-19

• document.write()

  The document.open(), document.write(), document.writeln(), and document.close() methods write content to a document, possibly while that document is still loading.

  Learn more

  • Chrome 45 Released on 2015-09-01
  • Chrome Android 45 Released on 2015-09-01
  • Edge 12 Released on 2015-07-29
  • Firefox 69 Released on 2019-09-03
  • Firefox for Android 79 Released on 2020-07-28
  • Safari 11 Released on 2017-09-19
  • Safari on iOS 11 Released on 2017-09-19

• escape() and unescape()

  The escape() and unescape() built-in Javascript methods encode and unencode strings using percent encoding, where certain characters are replaced by hexadecimal escape sequences.

  Learn more

  • Chrome 1 Released on 2008-12-11
  • Chrome Android 18 Released on 2012-06-27
  • Edge 12 Released on 2015-07-29
  • Firefox 1 Released on 2004-11-09
  • Firefox for Android 4 Released on 2011-03-29
  • Safari 1 Released on 2003-06-23
  • Safari on iOS 1 Released on 2007-06-29

• execCommand()

  The execCommand() method reads and writes from the clipboard and performs editing commands on editable text, such as changing the font name or style. Related methods check whether commands are supported, enabled, or applied.

  Learn more

  • Chrome 1 Released on 2008-12-11
  • Chrome Android 18 Released on 2012-06-27
  • Edge 12 Released on 2015-07-29
  • Firefox 69 Released on 2019-09-03
  • Firefox for Android 79 Released on 2020-07-28
  • Safari 1.3 Released on 2005-04-15
  • Safari on iOS 1 Released on 2007-06-29

• window.external

  The window.external.AddSearchProvider() and window.external.IsSearchProviderInstalled() do nothing. Historically, they added external search providers to the browser.

  Learn more

  • Chrome 9 Released on 2011-02-03
  • Chrome Android 18 Released on 2012-06-27
  • Edge 12 Released on 2015-07-29
  • Firefox 2 Released on 2006-10-24
  • Firefox for Android 4 Released on 2011-03-29
  • Safari Not supported
  • Safari on iOS Not supported

  Baseline availability blocked since July 2015 by Safari (132 months)

• Feature policy

  The Feature-Policy response header sets whether a policy-controlled feature, such as an API, may be used in a document. Not to be confused with permissions policy.

  Learn more

  • Chrome 74 Released on 2019-04-23
  • Chrome Android 74 Released on 2019-04-24
  • Edge 79 Released on 2020-01-15
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari Not supported
  • Safari on iOS Not supported

• Function caller and arguments

  The caller and arguments properties of a non-strict mode Function object are the function that called it and the arguments it was called with. Not to be confused with the arguments variable in a function body's local scope.

  Learn more

  • Chrome 1 Released on 2008-12-11
  • Chrome Android 18 Released on 2012-06-27
  • Edge 12 Released on 2015-07-29
  • Firefox 1 Released on 2004-11-09
  • Firefox for Android 4 Released on 2011-03-29
  • Safari 3 Released on 2007-10-26
  • Safari on iOS 1 Released on 2007-06-29

• glyph-orientation-vertical

  The glyph-orientation-vertical CSS property sets the orientation of glyphs in text rendered in a vertical writing mode.

  Learn more

  • Chrome Not supported
  • Chrome Android Not supported
  • Edge Not supported
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari 4 Released on 2009-06-08
  • Safari on iOS 3.2 Released on 2010-04-03

• :host-context()

  The :host-context() CSS pseudo-class selects the containing element of the shadow tree in which it is used if that element or an ancestor matches the provided selector.

  Learn more

  • Chrome 54 Released on 2016-10-12
  • Chrome Android 54 Released on 2016-10-19
  • Edge 79 Released on 2020-01-15
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari Not supported
  • Safari on iOS Not supported

• HTML wrapper methods

  JavaScript built-in methods such as, String.bold() and String.italics(), wrap strings in (often historic) HTML.

  Learn more

  • Chrome 1 Released on 2008-12-11
  • Chrome Android 18 Released on 2012-06-27
  • Edge 12 Released on 2015-07-29
  • Firefox 1 Released on 2004-11-09
  • Firefox for Android 4 Released on 2011-03-29
  • Safari 1 Released on 2003-06-23
  • Safari on iOS 1 Released on 2007-06-29

• ime-mode

  The ime-mode CSS property sets the state of the input method editor for text fields.

  Learn more

  • Chrome Not supported
  • Chrome Android Not supported
  • Edge Not supported
  • Firefox 3 Released on 2008-06-17
  • Firefox for Android 4 Released on 2011-03-29
  • Safari Not supported
  • Safari on iOS Not supported

• Import assertions

  Module import … assert { type: "json" } and import … assert { type: "css" } JavaScript statements load JSON and CSS data.

  Learn more

  • Chrome Not supported
  • Chrome Android Not supported
  • Edge Not supported
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari Not supported
  • Safari on iOS Not supported

• isInputPending()

  The navigator.scheduling.isInputPending() method checks if there are pending input events, such as touch or mouse events. This allows you to yield from long-running scripts that might be blocking user interaction.

  Learn more

  • Chrome 87 Released on 2020-11-17
  • Chrome Android 87 Released on 2020-11-17
  • Edge 87 Released on 2020-11-19
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari Not supported
  • Safari on iOS Not supported

• MathML Full

  MathML specifies several elements and attributes that are not included in MathML Core. Math applications outside of browsers may implement these features, but they are discouraged for web use.

  Learn more

  • Chrome Not supported
  • Chrome Android Not supported
  • Edge Not supported
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari Not supported
  • Safari on iOS Not supported

• MediaController

  The playback of multiple <video> or <audio> elements can be coordinated by a MediaController instance, for example to synchronize a sign-language interpreter track with the main video track.

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  • Chrome Not supported
  • Chrome Android Not supported
  • Edge Not supported
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari 7 Released on 2013-10-22
  • Safari on iOS 7 Released on 2013-09-18

• Mutation events

  Mutation events like DOMSubtreeModified, DOMNodeInserted, or DOMNodeRemoved fire when DOM changes occur.

  Learn more

  • Chrome Not supported
  • Chrome Android Not supported
  • Edge Not supported
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari Not supported
  • Safari on iOS Not supported

• overflow: overlay

  The overflow: overlay CSS declaration is an alias to overflow: auto. Historically, it caused non-standard behavior, allowing scrollbars to overlay content without taking up layout space.

  Learn more

  • Chrome 114 Released on 2023-05-30
  • Chrome Android 114 Released on 2023-05-30
  • Edge 114 Released on 2023-06-02
  • Firefox 112 Released on 2023-04-11
  • Firefox for Android 112 Released on 2023-04-11
  • Safari 12 Released on 2018-09-17
  • Safari on iOS 12 Released on 2018-09-17

• Page break aliases

  The page-break-before, page-break-inside, and page-break-after CSS properties are aliases to the break-before, break-inside, and break-after properties.

  Learn more

  • Chrome 1 Released on 2008-12-11
  • Chrome Android 18 Released on 2012-06-27
  • Edge 12 Released on 2015-07-29
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari Not supported
  • Safari on iOS Not supported

• PerformanceTiming and PerformanceNavigation

  The window.performance.timing and window.performance.navigation APIs report performance timing information for events that occur during the loading and use of the current page.

  Learn more

  • Chrome 56 Released on 2017-01-25
  • Chrome Android 56 Released on 2017-02-01
  • Edge 18 Released on 2018-10-02
  • Firefox 56 Released on 2017-09-28
  • Firefox for Android 56 Released on 2017-09-28
  • Safari 14.1 Released on 2021-04-26
  • Safari on iOS 14.5 Released on 2021-04-26

• Portals

  The <portal> HTML element embeds another page into the current page as a non-interactive preview.

  Learn more

  • Chrome Not supported
  • Chrome Android Not supported
  • Edge Not supported
  • Firefox Not supported Position: defer
  • Firefox for Android Not supported Position: defer
  • Safari Not supported
  • Safari on iOS Not supported

• Private network access

  The Access-Control-Request-Private-Network: true and Access-Control-Allow-Private-Network: true HTTP request and response headers establish permission for websites to make requests to internal networks, such as to routers.

  Learn more

  • Chrome Not supported
  • Chrome Android Not supported
  • Edge Not supported
  • Firefox Not supported Position: positive
  • Firefox for Android Not supported Position: positive
  • Safari Not supported
  • Safari on iOS Not supported

• Protected audience

  The protected audience API facilitates advertisement sales by allowing sites to register users as part of an interest group or to choose which ads appear based on those interest groups, while minimizing the ability of advertisers to track specific members of the interest group. Also known as FLEDGE.

  Learn more

  • Chrome 134 Released on 2025-03-04
  • Chrome Android 134 Released on 2025-03-04
  • Edge Not supported
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari Not supported
  • Safari on iOS Not supported

• __proto__

  The __proto__ property of objects partially exposes the prototype of an object.

  Learn more

  • Chrome 1 Released on 2008-12-11
  • Chrome Android 18 Released on 2012-06-27
  • Edge 12 Released on 2015-07-29
  • Firefox 1 Released on 2004-11-09
  • Firefox for Android 4 Released on 2011-03-29
  • Safari 3 Released on 2007-10-26
  • Safari on iOS 1 Released on 2007-06-29

• RegExp compile()

  The compile() method of RegExp objects recompiles an existing regular expression object using a new pattern and flags.

  Learn more

  • Chrome 1 Released on 2008-12-11
  • Chrome Android 18 Released on 2012-06-27
  • Edge 12 Released on 2015-07-29
  • Firefox 1 Released on 2004-11-09
  • Firefox for Android 4 Released on 2011-03-29
  • Safari 3.1 Released on 2008-03-18
  • Safari on iOS 2 Released on 2008-07-11

• RegExp static properties

  The RegExp object has several static properties to access the input and results of the most-recent regular expression match.

  Learn more

  • Chrome 1 Released on 2008-12-11
  • Chrome Android 18 Released on 2012-06-27
  • Edge 12 Released on 2015-07-29
  • Firefox 1 Released on 2004-11-09
  • Firefox for Android 4 Released on 2011-03-29
  • Safari 3 Released on 2007-10-26
  • Safari on iOS 1 Released on 2007-06-29

• Related website sets

  Related website sets declares relationships between sites so the browser allows cookie and storage access between them through methods such as document.requestStorageAccessFor().

  Learn more

  • Chrome 119 Released on 2023-10-31
  • Chrome Android 120 Released on 2023-12-05
  • Edge 119 Released on 2023-11-02
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari Not supported
  • Safari on iOS Not supported

• Intervention reports

  Intervention reporting sends a report to a URL nominated by the Reporting-Endpoints header when the browser has not honored an application's request, contrary to specified behavior, such as for security or privacy reasons.

  Learn more

  • Chrome 69 Released on 2018-09-04
  • Chrome Android 69 Released on 2018-09-04
  • Edge 79 Released on 2020-01-15
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari Not supported
  • Safari on iOS Not supported

• Shared storage

  The sharedStorage API stores data to a shared space where the data can then be processed without the ability to track users across the different sites they visit. A common use case is measuring the reach of third-party ads without using user-tracking cookies.

  Learn more

  • Chrome Not supported
  • Chrome Android Not supported
  • Edge Not supported
  • Firefox Not supported Position: negative
  • Firefox for Android Not supported Position: negative
  • Safari Not supported Position
  • Safari on iOS Not supported Position

• Shared storage locks

  The withLock option to set(), append(), delete(), clear(), and batchUpdate() methods of the sharedStorage API prevents duplicate reporting from cross-site race conditions.

  Learn more

  • Chrome 134 Released on 2025-03-04
  • Chrome Android 134 Released on 2025-03-04
  • Edge 134 Released on 2025-03-06
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari Not supported
  • Safari on iOS Not supported

• Speech recognition grammar

  The SpeechRecognition.grammars property of the Web Speech API represents a set of words or patterns of words that the recognition service should recognize, used for when the recognition service's accuracy is low.

  Learn more

  • Chrome Not supported
  • Chrome Android Not supported
  • Edge Not supported
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari Not supported
  • Safari on iOS Not supported

• SVG 1.1

  The SVG 1.1 image format has several components that were excluded from SVG 2, such as fonts, alternate glyphs, and the xlink namespace.

  Learn more

  • Chrome Not supported
  • Chrome Android Not supported
  • Edge Not supported
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari ≤13.1 Released before 2020-03-24
  • Safari on iOS ≤13.4 Released before 2020-03-24

• Table styling

  Attributes and properties of table elements, such as align, vAlign, noWrap, bgcolor, or char set various visual presentation properties of the table and its sections and cells.

  Learn more

  • Chrome Not supported
  • Chrome Android Not supported
  • Edge Not supported
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari Not supported
  • Safari on iOS Not supported

• :target-within

  The :target-within CSS pseudo-class matches the element with an ID matching the URL fragment and its ancestors.

  Learn more

  • Chrome Not supported
  • Chrome Android Not supported
  • Edge Not supported
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari Not supported
  • Safari on iOS Not supported

• text-decoration-line: blink

  The text-decoration: blink CSS declaration flashes text between visible and invisible.

  Learn more

  • Chrome 57 Released on 2017-03-09
  • Chrome Android 57 Released on 2017-03-16
  • Edge 79 Released on 2020-01-15
  • Firefox 36 Released on 2015-02-24
  • Firefox for Android 36 Released on 2015-02-27
  • Safari 12.1 Released on 2019-03-25
  • Safari on iOS 12.2 Released on 2019-03-25

• Topics

  The topics API reports a user's likely subject-matter interests (as determined by the browser, known as topics) to iframes. This allows for interest-based advertising that does not rely on user's exact browsing history, third-party cookies, or fingerprinting.

  Learn more

  • Chrome 126 Released on 2024-06-11
  • Chrome Android 126 Released on 2024-06-11
  • Edge 126 Released on 2024-06-13
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari Not supported
  • Safari on iOS Not supported

• WebVR

  The navigator.getVRDisplays() API represents virtual reality (VR) devices, including sensors and head-mounted displays.

  Learn more

  • Chrome Not supported
  • Chrome Android Not supported
  • Edge Not supported
  • Firefox Not supported
  • Firefox for Android Not supported
  • Safari Not supported
  • Safari on iOS Not supported

• with

  The with JavaScript statement adds a given object to the chain of scopes used to evaluate names.

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  • Chrome 38 Released on 2014-10-07
  • Chrome Android 38 Released on 2014-10-08
  • Edge 12 Released on 2015-07-29
  • Firefox 48 Released on 2016-08-02
  • Firefox for Android 48 Released on 2016-08-02
  • Safari 10 Released on 2016-09-20
  • Safari on iOS 10 Released on 2016-09-13

• word-break: break-word

  The word-break: break-word CSS declaration sets word breaks to occur according to their customary rules.

  Learn more

  • Chrome 1 Released on 2008-12-11
  • Chrome Android 18 Released on 2012-06-27
  • Edge 12 Released on 2015-07-29
  • Firefox 67 Released on 2019-05-21
  • Firefox for Android 67 Released on 2019-05-21
  • Safari 3 Released on 2007-10-26
  • Safari on iOS 2 Released on 2008-07-11

• writing-mode SVG 1.1 values

  The lr, lr-tb, rl, rl-tb, tb, and tb-rl keyword values for the writing-mode CSS property set the text direction for elements in SVG 1.1 documents.

  Learn more

  • Chrome 48 Released on 2016-01-20
  • Chrome Android 48 Released on 2016-01-26
  • Edge 12 Released on 2015-07-29
  • Firefox 43 Released on 2015-12-15
  • Firefox for Android 43 Released on 2015-12-15
  • Safari 10.1 Released on 2017-03-27
  • Safari on iOS 10.3 Released on 2017-03-27