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Firefox 49 release notes for developers

files/en-us/mozilla/firefox/releases/49/index.md

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To test the latest developer features of Firefox, install Firefox Developer Edition Firefox 49 was released on September 20, 2016. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.

Changes for web developers

Developer Tools

HTML

  • Added support for the {{HTMLElement("details")}} and {{HTMLElement("summary")}} elements (Firefox bug 1226455).
  • The pattern attribute of the {{HTMLElement("input")}} element now uses the 'u' parameter in the underlying JavaScript {{jsxref("RegExp")}} (Firefox bug 1227906).
  • To match a spec change, an invalid value of the kind attribute of the {{HTMLElement('track')}} element is now treated like "metadata" instead of "subtitles" (Firefox bug 1269712).
  • The {{HTMLElement("iframe")}} element's sandbox attribute now supports the 'allow-popups-to-escape-sandbox' and 'allow-modals' values (Firefox bug 1190641).
  • Support for microdata attributes and the Microdata API have been removed (Firefox bug 909633).
  • The referrerpolicy attribute on the {{HTMLElement("a")}} element now supports the 'no-referrer-when-downgrade' and 'origin-when-cross-origin' (Firefox bug 1178337).
  • The form content attribute of the {{HTMLElement("label")}} element has been removed. The {{domxref("HTMLLabelElement.form")}} property still exists, but now returns the form with which the label's control is associated, if there is a control (and if that control is associated with a form) (Firefox bug 1268852).

CSS

  • Added {{cssxref("background-position-x")}} and {{cssxref("background-position-y")}}, which allow separately specifying the horizontal and vertical offsets at which to draw a background image; these are components of {{cssxref("background-position")}} (Firefox bug 550426).

  • Added support for the round and space keywords to {{cssxref("background-repeat")}} (Firefox bug 548372).

  • On {{cssxref("background-clip")}}, the keyword text is now activated by default (Firefox bug 1264905).

  • Added support for specifying colors with an alpha channel using 4- and 8-digit CSS hex color values (#RRGGBBAA and #RGBA) (Firefox bug 567283).

  • The pseudo-class {{cssxref(":dir")}} has been unprefixed (Firefox bug 859301).

  • In our experimental implementation (not yet activated by default) of {{cssxref("clip-path")}}, we can now interpolate between {{cssxref("<basic-shape>")}} values (Firefox bug 1110460).

  • Added the q length unit (Firefox bug 1274526).

  • The property {{cssxref("text-align-last")}} has been unprefixed (Firefox bug 1039541).

  • Added support for {{cssxref("overflow-wrap")}}, replacing word-wrap that is still supported as an alternative name (Firefox bug 955857).

  • Our experimental CSS Grids implementation has been improved:

    • Implemented {{cssxref("<percentage>")}} for the grid-gap, grid-row-gap, and grid-column-gap properties (Firefox bug 1266268).
    • Implemented grid layout support for {{cssxref("align-self")}}, {{cssxref("justify-self")}} values baseline and last-baseline (aka "baseline self-alignment") (Firefox bug 1221525).
    • Implemented grid item baseline content alignment (Firefox bug 1256429).

  • Our experimental CSS Masks implementation has been improved:

    • The {{cssxref("mask-origin")}} property now uses border-box instead of padding-box as initial value, to match the spec (Firefox bug 1258286).
    • The {{cssxref("mask-repeat")}} property now supports the space and round values (Firefox bug 1258626).
    • Fixed an issue preventing the {{cssxref("mask-position")}} attribute from being animated (Firefox bug 1273804).

  • The preference controlling {{cssxref("text-emphasis")}} has been removed, so support for this property can no longer be disabled (Firefox bug 1229609).

JavaScript

Interfaces/APIs/DOM

DOM & HTML DOM

  • The method {{domxref("DOMTokenList.supports()")}} has been added (Firefox bug 1257849).
  • The {{domxref("DOMTokenList.replace()")}} method has been added (Firefox bug 1224186).
  • Leading '?' characters are now ignored in the parameter of the {{domxref("URLSearchParams.URLSearchParams", "URLSearchParams()")}} constructor (Firefox bug 1268361).
  • The value returned by {{domxref("URL.origin")}}, {{domxref("HTMLAnchorElement/origin", "HTMLAnchorElement.origin")}}, and {{domxref("HTMLAnchorElement/origin", "HTMLAreaElement.origin")}} for URL using the blob: scheme is no longer incorrectly null but is instead the origin of the URL formed by removing the leading blob: (Firefox bug 1270451).
  • In prerendering mode, the {{domxref('Document.visibilityState')}} property now returns 'prerender' (Firefox bug 1069772).
  • The {{domxref("Window.isSecureContext")}} property has been implemented (Firefox bug 1162772).
  • The DOM4 {{domxref("Element.before")}}, {{domxref("Element.after")}}, {{domxref("Element.replaceWith")}}, {{domxref("Element.append")}} and {{domxref("Element.prepend")}} methods have been implemented (Firefox bug 911477).
  • The TouchList.identifiedTouch() method has been removed (Firefox bug 1188539).
  • By default, the scrollbars {{domxref("Window")}} feature is enabled when calling {{domxref("Window.open()")}}. In the past, while it was strongly recommended to enable it, it wasn't the default (Firefox bug 1257887).
  • Added the experimental and non-standard {{domxref("HTMLMediaElement.seekToNextFrame()")}} method, which allows seeking frame-by-frame through video content (Firefox bug 1235301). While you're encouraged to experiment with this method to help us understand how useful it is, do not use it in production code!
  • The {{domxref("HTMLLabelElement.form")}} property now returns the form with which the label's control is associated, if there is a control (and if that control is associated with a form). Previously, labels were directly associated with forms using this property (Firefox bug 1268852).
  • Support for the third parameter of {{domxref("EventTarget.addEventListener()")}}, either a {{jsxref("Boolean")}} or an EventListenerOptions has been added (Firefox bug 1266164 and Firefox bug 1266066).
  • The audio volume related values for {{domxref("KeyboardEvent.key")}} have been renamed. "VolumeDown" is now "AudioVolumeDown", "VolumeUp" is now "AudioVolumeUp", and "VolumeMute" is now "AudioVolumeMute". This brings Firefox into alignment with the latest draft of the UI Events specification (Firefox bug 1272578). See Code values for keyboard events for a full list of available key codes.
  • The keys previously referred to as "MozHomeScreen", "MozCameraFocusAdjust", and "MozPhoneCall" now have official names in the UI Events specification: "GoHome", "CameraFocus", and "Call". Firefox 49 has been updated to use the new names (Firefox bug 1272599). See Code values for keyboard events for a full list of available key codes.
  • The key values "Separator" and "MediaSkip" have been removed, as they were deprecated and unused (Firefox bug 1232919).
  • Key values and the corresponding key codes "Hyper" and "Super" have been added to represent these legacy modifier keys (Firefox bug 1232919).
  • Two key values for multimedia numeric keypad keys have been added: "Key11" and "Key12" (Firefox bug 1232919).
  • The following new key values have been added for audio control keys: "AudioBassBoostToggle", "AudioTrebleDown", and "AudioTrebleUp" (Firefox bug 123919).
  • Key values have been added for these microphone control keys: MicrophoneToggle, MicrophoneVolumeDown, MicrophoneVolumeUp, and MicrophoneVolumeMute (Firefox bug 123919).
  • New key values have been added to support speech recognition devices: SpeechCorrectionList and SpeechInputToggle (Firefox bug 1232919).
  • New key values have been added to support special buttons on phones: AppSwitch, Call, CameraFocus, EndCall, GoBack, GoHome, HeadsetHook, LastNumberRedial, Notification, MannerMode, and VoiceDial (Firefox bug 1232919).
  • These new application key values have been added: LaunchContacts and LaunchPhone (Firefox bug 1232919).
  • New key values have been added to support television devices: TV3DMode, TVAntennaCable, TVAudioDescription, TVAudioDescriptionMixDown, TVAudioDescriptionMixUp, TVContentsMenu, TVDataService, TVInput, TVInputComponent1, TVInputComponent2, TVInputComposite1, TVInputComposite2, TVInputHDMI1, TVInputHDMI2, TVInputHDMI3, TVInputHDMI4, TVInputVGA1, TVMediaContext, TVNetwork, TVNumberEntry, TVRadioService, TVSatellite, TVSatelliteBS, TVSatelliteCS, TVSatelliteToggle, TVTerrestrialAnalog, TVTerrestrialDigital, TVTimer, and DVR (Firefox bug 1232919).
  • The key value MediaSelect has been replaced with the standard LaunchMediaPlayer key value (Firefox bug 1272592).
  • Additional media player key values have been added as well. These are MediaAudioTrack, MediaSkipBackward, MediaSkipForward, MediaStepBackward, MediaStepForward, MediaTopMenu, NavigateIn, NavigateNext, NavigateOut, and NavigatePrevious (Firefox bug 1232919).

Canvas

  • The {{domxref("CanvasRenderingContext2D.filter")}} property, which provides support for adding filters to a canvas, is now activated by default and no longer needs to be enabled using a preference (Firefox bug 1173545).

WebGL

  • The {{domxref("EXT_color_buffer_float")}} {{domxref("WebGL2RenderingContext", "WebGL 2", "", 1)}} extension has been implemented (Firefox bug 1129332).
  • The {{domxref("HTMLCanvasElement/webglcontextcreationerror_event", "webglcontextcreationerror")}} event, which is sent when a WebGL context creation attempt fails, has been implemented (Firefox bug 1271478). Use this to help understand what went wrong, both for debugging and for production error handling.

IndexedDB

  • You can now rename IndexedDB indexes; the {{domxref("IDBIndex.name")}} property is no longer read-only (Firefox bug 1118028).
  • You can also now rename {{domxref("IDBObjectStore")}}s; the {{domxref("IDBObjectStore.name")}} property is no longer read-only (Firefox bug 1118028).

Service Workers and related

  • The Fetch API's {{domxref("Response")}} object now implements the {{domxref("Response.redirected", "redirected")}} property, which indicates whether or not the response is for a request which was redirected. Please review the security related notes in the documentation before using this property (Firefox bug 1243792).
  • In the Permissions API, Firefox no longer supports the 'push' PermissionDescriptor dictionary type (referred to in the spec as PushPermissionDescriptor); this is because Firefox relies on a quota system for controlling the userVisibleOnly status instead, and was throwing an error when it encountered a PushPermissionDescriptor instance (Firefox bug 1266821). With this dictionary removed, Firefox now ignores it.

Media Streams

  • In the past, it was possible for a call to {{domxref("MediaDevices.getUserMedia()")}} which requests both audio and video to succeed in cases where the user has only one of the two types of hardware available. This has been fixed (Firefox bug 802326).
  • In prior versions of Firefox, it was possible for a call to {{domxref("MediaDevices.getUserMedia()")}} which requests both audio and video to succeed even though the user denied access to one but not both of the matching devices. This has been fixed (Firefox bug 802326). This involves minor user interface changes as well, to remove the options to choose "No audio" or "No video" when the user is prompted for permissions.
  • The {{domxref("MediaStream.getTrackById()")}} method has been implemented (Firefox bug 1208390).

WebRTC

  • The {{domxref("RTCPeerConnection.addTrack()")}} method has been updated to allow tracks which are not components of the specified streams to be added to the connection. Instead, the streams are used to group tracks on the receiving end of the connection (Firefox bug 1271669).

New APIs

  • The {{domxref("PerformanceObserver")}} API is now activated by default on Nightly. It is not available by default in other versions of Firefox 49 (Firefox bug 1271487).

Others

  • {{domxref("XMLHttpRequest.getResponseHeader()")}} and {{domxref("XMLHttpRequest.getAllResponseHeaders()")}} return empty headers in case the preference network.http.keep_empty_response_headers_as_empty_string is set to true (Firefox bug 669259).
  • The Firefox OS-only Data Store API has been removed (Firefox bug 1261009).
  • The Fullscreen API event handlers Document.onfullscreenchange and Document.onfullscreenerror have been removed from {{domxref("Element")}} as they were never fired there; the prefixed versions of these event handlers have been kept there for compatibility purposes, however (Firefox bug 1270386). Note that this is not yet activated by default, but is behind the full-screen-api.unprefix.enabled preference (Firefox bug 1268749).
  • The obsolete Document.mozFullScreen property has been unprefixed to {{domxref("Document.fullscreen")}} Firefox bug 1269157. Note that this is not yet activated by default by behind the full-screen-api.unprefix.enabled preference (Firefox bug 1268749).
  • The read-only properties {{domxref("Document/fullscreenElement", "Document.fullscreenElement")}} and {{domxref("Document.fullscreenEnabled")}} no longer throw an exception if an attempt is made to change their values; instead, the new value is silently ignored and the setter function is a no-op (Firefox bug 1269798).
  • Any kind of data can now be retrieved from the clipboard using {{domxref("DataTransfer.getData()")}}: previously, only data of certain MIME types were supported Firefox bug 860857.
  • Our implementation of the Frame Timing API, consisting of the two interfaces PerformanceCompositeTiming and PerformanceRenderTiming, has been removed as the spec has been completely rewritten (Firefox bug 1271846).
  • To match the spec, the {{domxref("VTTCue.positionAlign")}} property now returns a PositionAlign enum instead of an Align enum (Firefox bug 1276129).
  • The speech synthesis part of Web Speech API is now activated by default (Firefox bug 1268633).
  • The Performance Timeline API is now available by default in Nightly (though not in Aurora, Beta or Release).
  • The {{domxref("ServiceWorkerGlobalScope.install_event", "install")}} event, and the {{domxref("Window.appinstalled_event", "Window.oninstall")}} event handler, are now supported for Web Manifests (Firefox bug 1265279).
  • When using the {{domxref("BaseAudioContext/createPeriodicWave", "AudioContext.createPeriodicWave()")}} method of the Web Audio API, you can now specify whether the resulting periodic wave should be normalized by including a dictionary object as the third parameter, which includes a single parameter — {disableNormalization: true} (Firefox bug 1265405).
  • In the WebVTT API, {{domxref("VTTCue.positionAlign")}} now correctly returns a PositionAlignSetting enum as per spec; previously it returned an AlignSetting enum (Firefox bug 1276129).
  • The Speech Synthesis part of the Web Speech API is now enabled by default across all desktop browsers (Firefox bug 1268633).
  • The {{domxref("Animation.Animation()", "Animation()")}} constructor of the Web Animations API now accepts a null timeline (Firefox bug 1096776).
  • The {{domxref("KeyframeEffect")}} property {{domxref("KeyframeEffect.target", "target")}} is now supported in Firefox, if you have enabled Web Animations (Firefox bug 1067769).

MathML

No change.

SVG

  • Removed support for the deprecated <altGlyph>, <altGlyphDef> and <altGlyphItem> elements (Firefox bug 1260032).

Audio/Video

No change.

Plugins and Flash

Beginning in Firefox 49, Firefox, by default, blocks certain kinds of Flash content that aren't necessary for sites to function well. This behavior, controlled by the preference browser.safebrowsing.blockedURIs.enabled, helps to improve the performance of sites and Firefox in general without having significant impact on site usability. It also helps improve stability of the browsing experience by eliminating a major cause of crashes. The blocked Flash modules include several used just for fingerprinting purposes, as well as a number of "supercookie" modules, and in the future may be expanded to include more types of blocked modules. See Firefox bug 1275591 for details.

This marks the next step in the journey toward a plugin-free future. HTML is very close to the point where plugins will no longer be needed to get the job done.

HTTP

Networking

  • The Proxy Auto-Configuration (PAC) implementation has been updated. Now weekdayRange, dateRange, and timeRange support "reversed ranges", for example, weekdayRange("SAT", "MON") will evaluate true if the current day is Saturday, Sunday, or Monday (Firefox bug 1251332).

Security

  • The {{domxref("Window.isSecureContext")}} property, indicating whether a context is capable of using features that require secure contexts, has been implemented (Firefox bug 1162772).

Compatibility

In order to improve compatibility with existing content, Firefox now accepts some WebKit prefixed properties and attributes.

  • The following properties now also work prefixed with -webkit:

    • -webkit-align-items
    • -webkit-align-content
    • -webkit-align-self
    • -webkit-animation
    • -webkit-animation-delay
    • -webkit-animation-direction
    • -webkit-animation-duration
    • -webkit-animation-fill-mode
    • -webkit-animation-iteration-count
    • -webkit-animation-name
    • -webkit-animation-play-state
    • -webkit-animation-timing-function
    • -webkit-backface-visibility
    • -webkit-background-clip
    • -webkit-background-origin
    • -webkit-background-size
    • -webkit-border-bottom-left-radius
    • -webkit-border-bottom-right-radius
    • -webkit-border-image
    • -webkit-border-top-left-radius
    • -webkit-border-top-right-radius
    • -webkit-border-radius
    • -webkit-box-shadow
    • -webkit-filter
    • -webkit-flex
    • -webkit-flex-basis
    • -webkit-flex-direction
    • -webkit-flex-flow
    • -webkit-flex-grow
    • -webkit-flex-shrink
    • -webkit-flex-wrap
    • -webkit-justify-content
    • -webkit-order
    • -webkit-perspective
    • -webkit-perspective-origin
    • -webkit-text-size-adjust
    • -webkit-transform
    • -webkit-transform-origin
    • -webkit-transform-style
    • -webkit-transition
    • -webkit-transition-delay
    • -webkit-transition-duration
    • -webkit-transition-property
    • -webkit-transition-timing-function
    • -webkit-user-select

  • The following properties map to the equivalent prefixed property:

    • -webkit-box-flex
    • -webkit-box-ordinal-group
    • -webkit-box-orient
    • -webkit-box-align
    • -webkit-box-pack

  • For {{cssxref("<image>")}} values:

    • The following functions map to their unprefixed equivalents: -webkit-linear-gradient(), -webkit-radial-gradient(), -webkit-repeating-linear-gradient(), and -webkit-repeating-radial-gradient().
    • The outdated -webkit-gradient is supported (and translated to a regular gradient)

  • The following {{cssxref("display")}} values are translated:

    • -webkit-box to -moz-box
    • -webkit-flex to flex
    • -webkit-inline-box to inline-flex
    • -webkit-inline-flex to -moz-inline-flex

  • The following properties are supported (and don't map to any unprefixed equivalent):

    • {{cssxref("-webkit-text-fill-color")}}
    • {{cssxref("-webkit-text-stroke-color")}}
    • {{cssxref("-webkit-text-stroke-width")}}
    • {{cssxref("-webkit-text-stroke")}}

  • The WebKitCSSMatrix interface is an alias of {{domxref("DOMMatrix")}}

  • The following media query features have been implemented:

    • -webkit-min-device-pixel-ratio as an alias of min-resolution with the same value (in dppx), though this feature is disabled by default (behind about:config pref layout.css.prefixes.device-pixel-ratio-webkit)
    • -webkit-max-device-pixel-ratio as an alias of max-resolution of the same value (in dppx); this feature is also disabled by default, behind the same about:config pref.
    • -webkit-transform-3d always matching, indicating 3d transform support.

Changes for add-on and Mozilla developers

WebExtensions

  • Support for the {{WebExtAPIRef("history")}} has been added. This provides access to the browser history, with methods available for searching the history, getting information about previously-visited pages, and adding and removing history entries.
  • Added the {{WebExtAPIRef("tabs.removeCSS()")}} method to the tabs API. This method lets you remove CSS which was previously injected by calling {{WebExtAPIRef("tabs.insertCSS()")}}.

Interfaces

  • In {{domxref("EventTarget.addEventListener()")}}, the value mozSystemGroup, active only in code running in XBL or in Firefox's chrome, is a {{jsxref("Boolean")}} which indicates if the listener is added to the system group. (Firefox bug 1274520)

Other

No change.