Every place has a GIF size limit. Fit your clip under it.
An iPhone or screen-recording MOV turns into a GIF many times its size. Slack, GitHub, email and Discord each reject files over a certain size. Pick where it's going, then trade length, width, frame rate and colours until the meter goes green.
Open MP4, MKV, MOV, AVI, WMV, FLV, RealMedia, DVD VOB, camcorder MTS or almost anything else, and save it as any of 32 formats. The converting happens in this tab. Your video is never uploaded.
Each file is identified from its first bytes as soon as you add it. Once the engine is loaded it is read in full, so you see the real codecs, size and length before you convert.
MPEG-4 Part 14 on the ISO base media format. The safest choice when a file has to play anywhere.
ffmpeg -i input.mp4 -map 0:v:0 -map 0:a:0? -vf "scale=trunc(iw/2)*2:trunc(ih/2)*2" -c:v libx264 -preset veryfast -crf 23 -pix_fmt yuv420p -c:a aac -b:a 128k -ac 2 -f mp4 -movflags +faststart video.mp4Every frame has to be squeezed into a small palette. Smooth skies and skin turn into stripes unless the converter mixes nearby colours in a fine pattern: called dithering. It hides the banding but makes the file bigger, because patterns compress badly.
A MOV is Apple's video container, but what's inside varies a lot. What you shot it on decides the frame rate, the colours and how much trimming the GIF needs.
GIFs autoplay and loop almost everywhere, which is their only real advantage. When the destination accepts video, a short MP4 looks better at a tenth of the size.
Neighbouring tools for short, looping clips.