Why is this GIF's animation speed different in Firefox vs. IE?

Question

Oracle Enterprise Manager has a web interface that uses this GIF:

The odd thing about this GIF is that in Firefox (v9&10) it spins about twice as fast as in MSIE (v7&9).

Why does the animation speed change depending on the browser?

Answer 1

Your GIF animation contains 40 frames, with a 0.03 second delay specified between each frame. That should give it a nominal runtime of 1.2 seconds per loop, which matches what I'm seeing here in Firefox.

The problem seems to be that many browsers will ignore very short per-frame delays and replace them with a default delay (often 0.1 seconds). And the cutoff for what counts as a "very short" delay varies between browsers: Firefox apparently acceps anything down to 0.02 seconds per frame, while IE ignores delays below 0.06 seconds per frame.

My recommendation would be to increase the per-frame delay to 0.06 seconds (and to remove every second frame if you want the animation to run fast). That should give consistent speed in all major browsers.

Edit: I went and did that for you. Here are two versions of the animation with 0.06 seconds per frame: fast (20 frames, 1.2 sec/loop) and slow (40 frames, 2.4 sec/loop) . I also optimized the animations with GIFsicle, so they're quite a bit smaller than the original.

For more information, see:

• Frame Delay Times for Animated GIFs by Steve Humphrey

• Animated GIF Minimum Frame Delay Browser Compatibility Study by Jeremiah Johnson

• Trivia: Animated GIF Timing at EricLaw's IEInternals