Can I arrange it with a keyboard?

Yes. Focus a photo, then use arrow keys to pan it, and Shift and arrow keys to swap it with a neighbour.

How many photos can I use?

Up to 9. With 7 or 8, the 6-photo layouts use the first six, and the panel tells you so.

The longest edge is 1080, 2048 or 4096 px, and the other side follows from the canvas shape you pick.

No. Building your collage happens on your device. Nothing is sent to a server.

Photo collage

Arrange 2 to 9 photos in a clean grid, ready to share.

Runs on your device. Nothing is uploaded.