Changes for Web developers
- Mixed content blocking. Firefox will no longer load non-secure (http) resources on secure (https) pages (bug 834836).
- The standard syntax of CSP 1.0 policies are now implemented and enforced by default.
- A Network Panel has been added to the developer tools. This is more detailed view than the "Net" view option in the Web Console.
- Web Console has been renamed "Console", and includes the option to filter security errors/warnings.
- The new Toolbox Options lets you disable features, change light/dark theme, or enable Chrome/Remote debugging.
<blink>element support is now completely dropped. The
<blink>tag now implements the
HTMLUnknownElementinterface (bug 857820).
rangetype of the
<input type="range">) has been switched on by default (bug 841950).
Object.definePropertymethod can now be used to redefine the
lengthproperty of an
KeyboardEvent.keyis now supported, but only for non-printable keys (bug 842927).
DOMImplementation.createHTMLDocumentis now optional as per updated DOM specification.
- The ability to add a sidebar panel (
window.sidebar.addPanel) has been dropped (bug 691647).
- The unprefixed
Window.cancelAnimationFramemethods has been added (bug 704063). The unprefixed
DOMHighResTimeStampas argument; the prefixed version did, and still is, received a
- The text argument for
window.confirmis now optional (bug 861605).
HTMLMediaElement.initialTimeproperty, removed from the spec, is no more supported (bug 742537).
AnimationEvent()constructor has been added (bug 848293).
AnimationEvent.pseudoElementproperty has been implemented (bug 848293).
TransitionEvent()constructor has been added (bug 848291).
TransitionEvent.pseudoElementproperty has been implemented (bug 848291).
- The non-standard
AnimationEvent.initAnimationEvent()have been removed (bug 868751).
- Instead of including usernames in the
RTCIceServer.urlproperty (such as stun:firstname.lastname@example.org), you now need to use the new
- The blink effect for
text-decoration: blink;has no more effect, but is still a valid value (bug 857820).
::beforepseudo-elements are now flex items (bug 867454).
- The way to compute viewport units has been changed. In conjunction with
overflow:auto, space taken by eventual scrollbars is not substracted from the viewport, whereas in the case of
overflow:scroll, it is. (bug 811403)
- Negative widths for the
<mspace>element has been implemented (bug 717546).
<semantics>element now determines the visible child as described in the MathML3 specification.
Changes for addon and Mozilla developers
Firefox developer tools
Addons that overlay chrome://browser/content/debugger.xul must now overlay chrome://browser/content/devtools/debugger.xul. You may add references to both these files in chrome.manifest for compatibility.
- Firefox 22 for developers
- Firefox 21 for developers
- Firefox 20 for developers
- Firefox 19 for developers
- Firefox 18 for developers
- Firefox 17 for developers
- Firefox 16 for developers
- Firefox 15 for developers
- Firefox 14 for developers
- Firefox 13 for developers
- Firefox 12 for developers
- Firefox 11 for developers
- Firefox 10 for developers
- Firefox 9 for developers
- Firefox 8 for developers
- Firefox 7 for developers
- Firefox 6 for developers
- Firefox 5 for developers
- Firefox 4 for developers
- Firefox 3.6 for developers
- Firefox 3.5 for developers
- Firefox 3 for developers
- Firefox 2 for developers
- Firefox 1.5 for developers