files/en-us/mozilla/firefox/releases/64/index.md
This article provides information about the changes in Firefox 64 that will affect developers. Firefox 64 was released on December 11, 2018.
The Accessibility info-bar has been enhanced to include information about the color contrast ratio of text or images on the page (Firefox bug 1473037).
Responsive Design Mode device selection is now saved between sessions (Firefox bug 1248619).
Resources that are potentially affected by Tracking Protection are now indicated in the Network Monitor (Firefox bug 1333994).
The Web Console got improvements around entering and evaluating code:
Stepping in the JavaScript Debugger also had some improvements:
No changes.
pointer:coarse (Firefox bug 1035774). For any-pointer and any-hover implementation, see Firefox bug 1483111.prefers-reduced-motion media feature is now supported in Firefox for Android (Firefox bug 1478505).yellow 25%, yellow 50% can now be written yellow 25% 50% (Firefox bug 1352643).full-size-kana value (Firefox bug 1498148).-moz-appearance values (Firefox bug 1496720).list-item is now supported on {{htmlelement("legend")}} elements (Firefox bug 1486602).path()s, as usable in {{cssxref("offset-path")}}, are now animatable (Firefox bug 1486094).-webkit--prefixed pseudo-element, that pseudo-element no longer invalidates it (see Firefox bug 1424106 for the details, and Firefox bug 1486325 for enabling this feature).-moz-box and -moz-inline-box {{CSSxRef("display")}} values have been hidden from web content (Firefox bug 1496961).::-moz-tree pseudo-element has been hidden from web content (Firefox bug 1496961).layout.css.filters.enabled preference has been removed; CSS filters can no longer be disabled (Firefox bug 1408841).No changes.
WebAssembly.Global() constructor, if no value is specified a typed 0 value is used. This is specified by the DefaultValue algorithm (Firefox bug 1490286).A number of changes related to the {{domxref("Fullscreen_API", "Fullscreen API", "", "1")}} have been implemented:
The {{domxref("WebVR_API", "WebVR API", "", "1")}} (1.1) is now re-enabled in macOS (Firefox bug 1476091).
{{domxref("Window.screenLeft")}} and {{domxref("Window.screenTop")}} have been implemented, as aliases of {{domxref("Window.screenX")}} and {{domxref("Window.screenY")}} (Firefox bug 1498860).
The {{domxref("XMLHttpRequest.getAllResponseHeaders()")}} method now returns header names all in lowercase, as per spec (Firefox bug 1398718).
The legacy HTMLAllCollection interface has been updated as per recent spec updates (Firefox bug 1398354).
{{domxref("Navigator.buildID")}} now returns a fixed timestamp as a privacy measure (Firefox bug 583181).
The following {{domxref("Document.execCommand()")}} UI feature commands have been disabled by default (Firefox bug 1490641:
enableObjectResizingenableInlineTableEditingenableAbsolutePositionEditorRTCRtpEncodingParameters settings changed via {{domxref("RTCRtpSender.setParameters()")}} used to not update if the changes were made during a call. They will now update live, without renegotiation (Firefox bug 1253499).RTCIceCandidateStats.mozLocalTransport, which has now been deprecated (Firefox bug 1435789).media.getusermedia.agc_enabled (Firefox bug 1496714).dom.window.event.enabled) and disabled by default in release versions for now due to other issues that have been uncovered (Firefox bug 1493869). Note that this was actually done late in the Firefox 63 release cycle, but we are mentioning it here just in case.LocalMediaStream interface and its stop() method have been removed (Firefox bug 1258143). This method is no longer available with the deprecation of LocalMediaStream. See the Stopping a video stream section to learn how to stop an entire stream.AudioStreamTrack and VideoStreamTrack interfaces have been removed, as both have been deprecated for some time (Firefox bug 1377146). Their functionality has been merged into {{domxref("MediaStreamTrack")}}; tracks are now identified by the value of their {{domxref("MediaStreamTrack.kind", "kind")}} property, such as audio or video.No changes.
Marionette:, L10n:, or Addon: prefix (including singeTap) have been removed (Firefox bug 1504478, Firefox bug 1504940).Shift key events by using WebDriver:PerformActions didn't result in capitalized letters (Firefox bug 1405370).WebDriver:Navigate could cause an infinite hang if the tab's underlying content process is changed multiple times during that navigation (Firefox bug 1504807).about:newtab but about:blank (Firefox bug 1506643).A new API, {{WebExtAPIRef("menus.overrideContext()")}}, can be called from the contextmenu DOM event to set a custom context menu in extension pages. This API allows extensions to hide all default Firefox menu items in favor of providing a custom context menu UI. This context menu can consist of multiple top-level menu items from the extension, and may optionally include tab or bookmark context menu items from other extensions. See this blog post for more details.
showDefaults: false option, which can be used to hide the default context menu options, was implemented in (Firefox bug 1367160).documentURLPatterns can now be used to match a moz-extension:// document URL, even if {{WebExtAPIRef("menus.overrideContext()")}} is used. This way, it can reliably be used to restrict custom menu items to certain documents (Firefox bug 1498896).You can now restrict where context menus can appear in an add-on using the new viewTypes property in {{WebExtAPIRef("menus.create()")}} and {{WebExtAPIRef("menus.update()")}} (Firefox bug 1416839).
{{WebExtAPIRef("menus.update()")}} can now be used to update the icon of an existing menu item (Firefox bug 1414566).
Extensions can now detect which mouse button was used when a menu item was clicked — this can be found using the new button property of {{WebExtAPIRef("menus.OnClickData")}} (Firefox bug 1469148).
cookieStoreId — which specifies the CookieStoreId to use for all tabs that were created when the window is opened (Firefox bug 1393570).cookieConfig property is an object that can accept a behavior property — this property can now take a new value, reject_trackers, which instructs the extension to reject tracking cookies (Firefox bug 1493057).devtools.panels.elements Sidebar.setPage() method is now supported (Firefox bug 1398734).pinned property of the page_action manifest key enables extensions to control whether their page actions should be pinned to the location bar on install or not (Firefox bug 1494135).chrome_settings_overrides field's search_provider object can now include new properties — suggest_url and suggest_url_post_params (Firefox bug 1486819), and search_url_post_params.