The security add-on for Firefox called HTTPS Everywhere (download) that forces HTTPS encryption on numerous popular websites has graduated to its first stable release, about a year after it was released into public beta.
The tool does not let you force HTTPS (Hypertext Transfer Protocol Secure) willy-nilly on websites. Instead, it includes a series of rules that supports sites that allow HTTPS encryption. The Electronic Frontier Foundation (EFF) said in the blog post announcing the release that it encompasses more than 1000 popular sites, including Google Search, Wikipedia, Twitter, Facebook, bit.ly, GMX, Wordpress.com blogs, The New York Times, Paypal, EFF.org, Tor and Ixquick. The extension was co-developed between the EFF and The TOR Project, which is a web service that encrypts data transmitted to and from your computer.
Not only is HTTPS Everywhere site-dependent, even sites that it works for might have some content that slips out of the encryption. The best way to check this, the EFF wrote, is to ensure that your browser's lock icon isn't broken or carrying an exclamation mark. "However, the effort that would be required to eavesdrop on your browsing should still be usefully increased," the blog post said.