Center-crop any photo to a circle or square avatar at a chosen size, then download. Runs in your browser.
The largest centered square of your photo is taken, scaled to your chosen size, and (for circle) clipped to a circle with a transparent background.
So a circular avatar has clean transparent corners and sits nicely on any background, like profile pictures and chat apps.
This tool center-crops automatically. For off-center crops, pre-crop with the image crop tool first.