Errr, firebug was a copy of IE developer toolbar, which was released at least a year before firebug. I think the original IE Dev toolbar beta release was in 2005, maybe 2006? While firebug came out 2007ish. Looks like MS has finally shut down the blog originally announcing it so can't link to it any more.
IE developer toolbar was actually better for quite a while too.
copy implies being of equivalent quality, I seem to remember Firebug being significantly better, although maybe I didn't use the absolutely first version.
It definitely wasn't, it lacked a lot of features of IE Dev toolbar, as far as I remember. Took a few years before it was better, MS let the Dev toolbar drift for a while, and Firebug overtook it. They also didn't promote the toolbar much, which meant a lot of people thought firebug was a revolutionary idea. I seem to remember, and could be wrong as it's a long time ago now, that IE Dev Toolbar's JavaScript support was much better.
Then Chrome came out and most people switched to that, partially as the Dev tools were great, although, again, initially lacked some features so I tended to use a mix of both for about a year. But Google iterated fast and firebug got clunky.
Ok, guess I'll take your word for it, I don't remember when I started with firebug exactly - probably not a super-early adopter though, I tend to let things mature for a bit before using.
Of course it wasn't as IE Dev toolbar was so much worse than Firebug. For example all unhandled exceptions from event handlers would show up in IE Dev toolbar as originated at row 0, column 0 and helpfully showing you the beginning of a JS script. I've wasted _days_ finding out bugs using that wretched tool.
IE developer toolbar was actually better for quite a while too.