- 
NEW
Built-in PDF viewer
- 
CHANGED
Canvas elements can export their content as an image blob using canvas.toBlob()
- 
CHANGED
Startup performance improvements (bugs 715402 and 756313)
- 
CHANGED
Experience better image quality with our new HTML scaling algorithm
- 
DEVELOPER
Debugger now supports pausing on exceptions and hiding non-enumerable properties
- 
DEVELOPER
Remote Web Console is available for connecting to Firefox on Android or Firefox OS (experimental, set devtools.debugger.remote-enabled to true)
- 
DEVELOPER
There is now a Browser Debugger available for add-on and browser developers (experimental, set devtools.chrome.enabled to true)
- 
DEVELOPER
Web Console CSS links now open in the Style Editor
- 
HTML5
CSS @page is now supported
- 
HTML5
CSS viewport-percentage length units implemented (vh, vw, vmin and vmax)
- 
HTML5
CSS text-transform now supports full-width
- 
FIXED
Certain valid WebGL drawing operations are incorrectly rejected, leaving incomplete rendering in affected pages (825205)
- 
FIXED
Starting Firefox with -private flag incorrectly claims you are not in Private Browsing mode (802274)
- 
FIXED
Plugins stop rendering when the top half of the plugin is scrolled off the top of the page, in HiDPI mode (825734)
What’s New
Known Issues
- 
                        Unresolved
                    
If you try to start Firefox using a locked profile, it will crash (see 573369)
- 
                        Unresolved
                    
For some users, scrolling in the main GMail window will be slower than usual (see 579260)
- 
                        Unresolved
                    
Mootools 1.2.x incompatible with Firefox 18 and newer.Fixed in Mootools 1.3 and newer (see 789036)
- 
                        Unresolved
                    
Some function keys may not work when pressed (see 833719)Unresolved on v19 Resolved in v21
 Notes (First offered to release channel users on February 19, 2013)
        Notes (First offered to release channel users on February 19, 2013)