It’s taken about 6 months, but Mozilla has managed to officially Retina-ize its Firefox browser on the Mac. A beta release of Firefox brought Retina support back in November 2012, but today’s public release of version 18 brings it to the masses.
Viewing the web in a non-Retina browser on one of the new MacBooks is straight painful. Graphics look pixelated, and text looks dull.
The 15-inch Retina MacBook Pro came out last June, and Firefox is the last major browser to add compatibility.
You can download Firefox 18 from the Mozilla website. The update can also be downloaded in the background for existing users.
Source: The Mozilla Blog