The concept of rapid releases established by Google Chrome prompted Mozilla to do the same for its Firefox browser. On June 21, 2011, Firefox 5.0 was the first rapid release for this browser, finished a mere six weeks after the previous edition. Mozilla created four more whole-number versions throughout the year, finishing with Firefox 9 on December 20, 2011. For those desiring long-term support, Mozilla made an Extended Support Release (ESR) version of Firefox 10 on January 31, 2012. Contrary to the regular version, a Firefox ESR receives regular security updates plus occasional new features and performance updates for approximately one year, after which a 12-week grace period is given before discontinuing that version number. Those who continued to use the rapid releases with an active Internet connection were automatically updated to Firefox 11 on March 15, 2012. By the end of 2011, however, Chrome overtook Firefox to become world's most used browser, and the competition between Chrome and Firefox intensified.