# Undoing changes

Almost every change to an image can be undone using the Edit > Undo command; an undone command can similarly be redone by using the Edit > Redo command. The number of operations that can be undone is limited only by your computer's memory. If you find that operations are slowing down, (or if your physical memory is filled up) you can use the commands under Edit > Purge to clear the undo buffer, thereby freeing memory.