This addition to Microsoft Internet Explorer 5 or later adds Google's searching capabilities in a toolbar in the web browser. The latest version includes pop-up ads blocking, automatic filling of forms, the ability to show the Google PageRank value for the current page being viewed, and spell checker, AutoLink and the Word Translator. It has been criticized for being a security risk because it updates itself without user intervention.
Other browsers, such as Mozilla, Mozilla Firefox, Opera, and Safari, have built-in search tools that offer the same functionality. Recently, Google also launched a new version of the toolbar, "Google Toolbar for Firefox", which functions similarly to its Internet Explorer counterpart, except it has exclusive Firefox-only features. There is also the well established Googlebar project, which although unofficial and not developed by Google directly offers very similar functionality to the official Google Toolbar.
The official Google toolbar for Firefox was discontinued by Google in 2011, and the unofficial Googlebar project hasn't been updated in years, and it did not include such functionality as PageRank or Google Bookmarks. As of July 2011, there is no Google toolbar for the current version of Firefox.