Is it just me, or is Firefox behaving more like a lead weight than a web browser lately? Since about version 26, any time I browse a media-heavy site, Firefox starts consuming all my CPU, and doing a ton of I/O. This usually calms down after a while, but it’s extremely annoying.

Sometimes the excessive CPU use is associated with playing Flash videos, in which case a task viewer will usually show that it’s the plugin container and the Flash plugin that are consuming all the CPU. But that’s not always the case.

The Flash plugin seems to crash a lot these days as well. Like every other time I play a video in Firefox. Normally, I’d be happy to blame Adobe, but I’m not convinced it’s their fault this time, because Flash is currently working fine in my other browsers.

One other annoyance in recent versions of Firefox is the way animated GIFs play. They stop, start again, play really fast, then really slow, and so on. Eventually they seem to settle down, but it takes a while.

Is anyone else seeing these problems?

Update 2014Mar11: Disabling all my add-ons seems to have resolved this problem. Now to identify which one.