Mozilla has released Firefox 21 on May 14th, 2013. New in this release include:

• The Social API now supports multiple providers
• Enhanced three-state UI for Do Not Track (DNT)
• Firefox will suggest how to improve your application startup time if needed
• Preliminary implementation of Firefox Health Report

See the Release Notes for more details and complete list of changes.

Also released was an update for Firefox 17esr (Firefox for Organization) with 17.0.6esr. The Firefox esr update only contains bug fixes and security/stability updates.

Depending on the operating system and update settings (Tools > Options… > Advanced > Update Tab), users will be prompted to update within in the next 48-hours. Windows users can also go to Help > About Firefox and click the Check for Updates button. Users may also manually download and install Firefox via getfirefox.com. The next scheduled releases will be Firefox 22.0 and 17.0.7esr on June 25th, 2013.