This article provides information about the changes in Firefox 71 that will affect developers. Firefox 71 was released on December 3, 2019.
Changes for web developers
- The Console's multi-line mode is now available by default.
- Console configuration options are now combined in a new toolbar settings menu (bug 1523868).
- Inline variable preview has been enabled (bug 1576679).
- Logging on events is now available (bug 1110276), as is the ability to filter by event type.
- The new debugger paused overlay can now be disabled using the
devtools.debugger.features.overlaypref (bug 1579768).
- We've got new keyboard shortcuts for opening the debugger: Ctrl + Shift + Z on Linux/Windows and Cmd + Opt + Z on macOS (bug 1583042).
- Pausing on a DOM Mutation Breakpoints now mentions the DOM node that has the breakpoint and, if available, the child node that was added/removed (bug 1576145).
- Locations in pretty printed sources are now correct after pretty-printing and when jumping to the source from the Inspector's events listener tooltip (bug 1500222).
- The Web sockets inspector is now enabled by default (bug 1573805).
- You can now do a full text search of request/response bodies, headers, and cookies.
- You can now enter patterns to block specific URLs from loading.
- The Timings tab now exposes timing data sent in the
Server-Timingheader (bug 1403051).
- Color swatches are now shown next to CSS variable definitions that have color values (bug 1456167).
:visitedstyles are now shown in the CSS rules view (bug 713106).
- Added the subgrid value from CSS Grid Level 2 to
- Added support for the
column-spanproperty to Multiple-column Layout (bug 1426010)
- Added support for the
- Mapped the
widthHTML attributes on the
<img>element to an internal
aspect-ratioproperty (bug 1585637). See the guide to this feature on MDN.
Promise.allSettled()method is now supported (bug 1549176). This method lets you easily wait until every promise in a set of promises has either resolved or rejected before running further code.
Array.from()and then use standard array methods.
- MathML elements now implement a MathML DOM and their class is
MathMLElement. With a proper MathML DOM, you can now use
mathmlEl.style, or global event handlers, for example. Prior to this change, MathML elements only implemented the
Elementclass (bug 1571487).
The Media Session API is now partially implemented. This API provides a standard mechanism for your content to share with the underlying operating system information about the state of media it's playing. This includes metadata such as artist, album, and track name, as well as potentially album artwork (bug 1580602).
The API also provides a way to receive notifications when the device's media controls (such as play, pause, and seek buttons) are activated by the user. To that end, the
MediaSession interface is now partially implemented, with support for setting and fetching the currently-playing media's metadata. and for the
setActionHandler() method. To access the
MediaSession API, use the
StaticRange()constructor is now supported (bug 1575980).
- The MathML
MathMLElementinterface has been implemented (bug 1571487).
Media, Web Audio, and WebRTC
MediaRecorderinterface now implements the
videoBitsPerSecondproperties (bug 1514158).
Canvas and WebGL
OES_fbo_render_mipmapWebGL extensions are now exposed by default (bug 1584277, bug 1583878).
WebDriver conformance (Marionette)
- Both the
WebDriver:TakeElementScreenshotcommands have been updated to respect the unhandled prompt behavior setting (bug 1584927).
- The command
Marionette:Quithas been updated to also allow quitting or restarting of other Gecko-driven applications besides Firefox (bug 1298921).
- For GeckoView-based browsers on Android, the returned
browserNamein the session capabilities will now always be
Changes for add-on developers
downloads.downloadnow identifies and reports as errors the following HTTP response codes:
- 404 returning
- 403 returning
- 402 and Proxy 407 returning
- Anything else above 400 returning
- 404 returning
downloads.downloadnow includes the optional
allowHttpErrors. When set to
booleanflag enables a download to continue after encountering an HTTP error. When set to
false, a download is canceled when an HTTP error is encountered. Default value:
false. (bug 1578955)
proxy.unregister()functions have been removed (bug 1443259).
proxy.onRequestshould now be used to handle the proxying of requests.
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