Gifski and Giffiti both turn video into GIFs on a Mac, and both are free. The difference is how far each one goes.
Gifski: a converter, and proud of it
Gifski is built around a respected GIF encoder that squeezes thousands of colours into each frame, so gradients and photos look remarkably smooth. The Mac app trims, crops, sets dimensions and speed, loops or bounces, and previews before converting. It also works with Shortcuts and the share menu. Its makers say plainly that it is a converter and will never add text or elements to a GIF.
Giffiti: an editor
Giffiti picks up where a converter stops. Captions that move, a multi-track timeline, keyframes, transitions, effects and cinemagraphs. It also records your screen and camera, exports formats beyond GIF, and can fit a GIF under a set size.
The short version
For the cleanest possible straight conversion, Gifski is excellent. When the GIF needs text, layers or effects, choose Giffiti.