Cropping is also compression
Cutting away half the frame removes half the pixels from every frame at once, so the file falls accordingly. On a screen recording that captured a whole desktop when only one window mattered, cropping is usually a bigger win than any compression setting.
The same rectangle is taken from every frame, so anything that moves out of that rectangle disappears mid-animation — worth scrubbing through before committing.
Choosing what to cut
Browser chrome, taskbars and desktop wallpaper carry no information and cost real bytes on every frame. A tight crop around the thing being demonstrated reads better in a README or a chat, where the GIF will be displayed small.
Cropping then resizing
Crop first, resize second. Cropping decides the composition; resizing decides the size. Doing it the other way round means resizing pixels you are about to throw away, and the visible result is slightly softer.
Frequently asked questions
Does cropping keep the animation?
Yes — every frame is cropped identically and the timing and loop settings are preserved.
Will it reduce the file size?
Yes, roughly in proportion to the area removed, because the saving applies to every frame. Cropping a wide screen recording down to one window often halves it.
Something disappears part-way through. Why?
It moved outside the crop rectangle. The same area is taken from every frame, so check the whole animation, not just the first frame, before cropping.
Should I crop or resize first?
Crop first. Then resize what is left, so you are not resampling pixels you were going to discard.
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