Users who turn on the feature can send and receive Facebook instant messages using the Messenger app from any page on the Web. They can also see their Facebook notifications. Users have the option to hide the sidebar if they’re not using it.
“As social sites have become a key part of people’s online lives, we want to make it easier to use the Web the way you want,” Mozilla said.
The technology uses an HTML5-based Social API that Mozilla and Facebook worked on together.
Mozilla will likely soon roll out similar features for Twitter and other social networks.
“Today’s Facebook integration is just the start of making Firefox more social. We’ll soon add support for more features and multiple providers,” Mozilla said in a blog post.