The Undo History command activates the Undo History dialog, which shows you thumbnails representing the operations you have done so far on the current image. This overview makes it easier for you to undo steps or to redo them.

Use the arrows for Undo and Redo, or simply click on the thumbnail, to bring the image back to a previous state. This is especially useful when you are working on a difficult task, where you often need to undo several steps at once. It is much easier to click on step 10 than to type Ctrl+Z ten times.

The “Clear undo History” command may be useful if you are working on a complex image and you want to free some memory.