The Gmail frontend is written in javascript using the closure library.

http://code.google.com/closure/

You can look at the (compiled version) of the code by looking at the scripts tab of the chrome web inspecter. They're there :)

Javascript on Gmail predates GWT. It may be possible that they've moved it to GWT but I don't think so, it loads too fast for starters.

For GWT normally you have to import the libraries, and then you get a lot of gibberish that looks like its been run through an obfuscator. Then in the body you have a section where you basically say 'insert stuff here', and that is where all your controls get inserted (by the magic javascript). Gmail doesn't have either of those that I can see.

I had a look at the source of gmail, and it looks like a normal page (lots of standard html controls (which you wouldn't expect to see in GWT) plus some weird ass timezone javascript at the end of it. Which does look kind of obfuscated, but probably was just run through a variable-name-shortener.

What I don't see, is any other script or onclick= stuff. And that is kind of suspicious. There's a blank script tag in the header, maybe they have a javascript that runs (to add all that junk dynamically) and then somehow erases itself (a neat trick?) or they have some other way of hiding the javascript?

You can find much of the code used to generate gmail's javascript here: http://code.google.com/closure/

We released this all some time ago under apache 2.