From phone video to GIF
GIFs work where videos do not autoplay: in many chat apps, email newsletters, GitHub issues, wikis and slide decks. Open the MP4, drag the handles to the moment you want, preview it with Play selection and press Make GIF.
Screen recordings of software make excellent GIFs for documentation and bug reports; keep them short and narrow, for example 640 pixels at 10 frames per second, to keep the size down.
Quality tips
Clips with large flat areas, such as screen recordings, compress much better than busy camera footage. If the file is too big, lower the width first, then the frame rate.
About MP4
MP4 is the most common video format, recorded by phones and cameras and used by most websites.
About GIF
GIF is an animated image format supported everywhere, from chats to email. It has 256 colors per frame and plays in a loop.