When Firebug was first released back in the good old days, there were not many comparable web development extensions available.
Web browsers did not ship with Developer Tools included, and Chrome was not even born yet. This changed over the years, and nearly every browser ships with its set of dev tools included nowadays.
Firebug on the other hand as been in development ever since, and while it still offers several interesting features, some core mechanics of it were lacking.
Older versions of the add-on used Firefox's debugging engine JSD1 for example which slowed down the browser significantly. Mozilla removed the debugging engine in Firefox 30 which is one reason why the new version of Firebug got released by the development team.
Firebug 2.0 changes that by switching over to the new debugging engine JSD2 which means that performance related issues in this regard should be a thing of the past.
But that is just one new feature of the new version. You can check out the official release notes to go through them all if you want, or take a look at the list of major new features, improvements and changes below.
- The EventBug extension for Dom Events has been integrated into the add-on.
- The HTML panel search has been improved. It supports regular expressions and CSS selectors now.
- Code auto complete has been improved as well. It is now available in the editor within the console panel. Press Tab to open suggestions on the screen.
- Logs can now be grouped in the console.
- You can now show or hide specific Firebug 2.0 panels, e.g. remove Cookies or Script.
- A new Color as authored option under CSS is now available to compare style information with the output of the browser.
- Options to create new HTML attributes faster. To do so, hover the mouse cursor over the closing bracket and click on it. This opens an inline editor that you can use to add an attribute.
- The command history is now limited to improve visibility.
- The Quick Info box of the Inspector can now be pinned.
When you install Firebug, it will take over the default Firefox Developer Tools shortcut (F12).
Firebug 2.0 adds several interesting new features to the web development extension, especially the upgrade to the new engine should improve performance of the add-on for users.