With Firefox 12 out the door, Mozilla is turning its efforts to polishing up Firefox 13, due out six weeks from now. If you don’t want to wait that long, you can download Firefox 13 from the beta release channel today.

Perhaps the best new feature in Firefox 13 is what’s known as “tabs on demand.” Tabs on demand refers to the way Firefox restarts when you have multiple tabs open. Firefox will now only restore the currently selected tab; background tabs are not loaded. Tabs on demand is a welcome relief for those of us who browse with dozens of tabs open all the time. You no longer need to fear restarting the browser since you won’t have to wait while every tab reloads. Instead, tabs will load only when you select them.

Firefox 13 will bring a slightly new look to some parts of the browser. Both the New Tab and the Home Page have been redesigned. The New Tab page now has links to your most recently and frequently visited sites. It looks more or less just like Opera’s Speed Dial, which Chrome also mimics. There’s an option to pin your favorite sites, as well as a button for rejecting sites you don’t want to see.

The default Home Page now has links to menu items like Bookmarks, History, Settings, Add-ons, Downloads and Sync Preferences. There’s nothing here that you can’t access from the menu bar, but it makes frequently used menu items easier for newcomers to find.

Web developers will be glad to know that Firefox 13 introduces support for Google’s not-quite-yet-a-standard SPDY protocol (technically the last two Firefox releases have supported SPDY, but this is the first to have it enabled by default). The SPDY protocol improves on HTTP and in many cases can significantly reduce page load times. SPDY’s other main advantage over HTTP is that all traffic is encrypted. Once Firefox 13 and the Opera 12 preview arrive in their final forms the majority of desktop browsers on the Web will support SPDY.

The Firefox 13 beta also brings a number of improvements to the new Developer Tools. For example, the Page Inspector now allows you to lock in CSS pseudo-classes on inspected page elements—handy for checking out what’s happening in a :hover code block.

For more details on everything that’s new in the developer tools and the rest of Firefox 13, check out Mozilla’s release notes.