Greasemonkey Hacks

Hack #63. Compose Your Mail in Gmail

Make mailto: links open the Gmail compose page.

The Web comprises many kinds of resources: web pages, newsgroups, IRC channels, FTP sites, and so on. Each kind of resource has a scheme, such as the http: in http://mozilla.org or the irc: in irc://irc.mozilla.org/firefox.

You've probably seen mailto: links on contact pages; when you click the link, it launches an external email program.

But what if you use a web mail service such as Gmail? Normally, getting mailto: links to launch a web-based email application is nontrivial. You would basically need to write an external mail program that switched back to your browser and opened the appropriate URL. What a pain! This hack solves the problem another way, by rewriting mailto: links to point to the Gmail Compose page.

The Code

This user script runs on all pages. From a high-level view, it sounds deceptively simple. Just find all the mailto: links, parse them, and replace them with links to Gmail. When you click the link, the browser just redirects to the Gmail Compose page instead of launching a separate application.

Of course, it's not really that simple. The problem is that mailto: links can be complex. RFC 2368, entitled "The mailto URL scheme," specifies the format. The overall structure is mailto:<recipient>?<querystring>, where <querystring> is a list of <name>=<value> pairs separated by ampersands (&). We want to pass these name/value pairs to Gmail, but, of course, Gmail's Compose page uses a different ...