Rotate Image

A quarter turn moves whole pixels to new positions without recalculating any of them, so nothing is resampled and nothing softens. A custom angle cannot work that way, because the pixels no longer land on the grid, so they are interpolated from their neighbours; this costs a little sharpness and is unavoidable at any angle that is not a multiple of 90. The picture turns inside its original frame, which is what straightening needs: the tilted edges run off the frame, and the small gaps left at the corners are transparent in PNG and WebP, or filled with a colour you choose in JPG.

Where it stops: Saving as JPG or WebP compresses the picture again, which costs a little quality even after a quarter turn; choose PNG as the output format when every pixel has to survive. A custom angle costs a little sharpness as well, and rotating the same image repeatedly compounds both, so rotate from the original rather than re-rotating your output. A tilted picture also loses its corners, because a tilted rectangle does not fit inside an upright one of the same size: crop the result afterwards for clean edges. HEIC and TIFF files, which browsers cannot open, are rotated on our service instead, where the canvas grows to fit the whole picture.