Templates that do the layout thinking
A good collage is a layout problem, and templates solve it: a hero photo with a strip of supporting shots, a clean 2×2, a 3×3 wall. Pick one, drop your photos, and each is centre-cropped to fill its cell exactly — mixed sizes and orientations line up automatically, nothing gets stretched.
Output is full social resolution (2000px square, story and wide shapes included) with no watermark, rendered on your own device. For side-by-side comparisons without cropping, Combine Images is the better fit; to go the other way and split one photo into grid tiles, there's the Image Splitter.