Xalomon

Their AI Photo Edit Background feature is extraordinary as it can be used as an unlimited tool to outpaint and uncrop your pictures! Just add a transparent background that goes beyond its canvas size, upload it, click original and use their Eraser to erase within the transparent area, then use a prompt that tells it what you want the extended area to be filled with. And that's it! I'll give you 4 great options of uncrops, this feature alone deserves 5 stars, though of course they have many other useful features too!