Video to GIF Maker — MP4, MOV, WebM

A browser will not simply hand over "frame 147" of an MP4. What it will do is seek a video element to a timestamp and let you copy the displayed picture. That is the path used here: seek, wait for the seek to settle, capture, repeat.

It is not the fastest approach available — WebCodecs is — but WebCodecs also requires unpacking the container yourself, and support for the codecs inside varies by browser and platform. Seeking works everywhere, which matters more than raw speed when the alternative is a conversion that fails outright.

Frame rate multiplies file size almost linearly, and GIF cannot represent arbitrary rates anyway. 12.5 fps is a good default for talking heads and UI recordings; 20 to 25 fps is worth the bytes for fast motion; anything above 25 mostly buys you a bigger file.

The size estimate updates as you change it, and it is measured rather than guessed — sample frames are genuinely encoded and the result is extrapolated across the timeline. If the number looks wrong, halve the frame rate before you touch the colour count; motion is usually the expensive part.