Firefox 18 comes with mostly under-the-hood updates
The changelogs also point out performance improvements around tab switching and better image quality with a new HTML scaling algorithm. There are also some changes for the developer, like support for a new DOM property—window.devicePixelRatio—and improvement in startup time through better handling of extension certificates.
The Android version of the browser also sees some upgrades, such as integration with Google Now, the ability to enable Safe Browsing, support for new fonts delivered through the browser and an option to opt-in for search suggestions when entering text into the Awesome Bar.
While the beta releases of Firefox 18 had a built-in PDF viewer, it is absent from the final release. It is possible that Mozilla deemed it incomplete and decided to delay it till the next release.
The last update for the browser was in November. The biggest feature of this update, numbered at 17, was the debut of the Social API. Firefox 17 was launched with Facebook messenger, which allowed social networking websites to add a persistent sidebar access to their sites.
The Social API is a completely opt-in feature on Firefox where users can themselves activate Facebook Messenger by going to the Facebook Messenger for Firefox page and clicking ‘Turn On.’ Once activated, a new social sidebar with chat and updates like tags and comments appear. In cases of messages and friend requests, a notification will be triggered where you can respond to the same right from the toolbar. A new ‘like’ button has also been added to the URL bar for sharing websites that don’t have their own ‘Like’ buttons yet.
Todd Simpson, Mozilla's Chief of Innovation, has said that the API is an open one and that even though Facebook is a lead partner, any other social provider or other type of service can implement to the API. “We believe it will have good use for financial, news, sports, email, or things other than traditional social,” he said.