Changing the default number of steps that the History palette displays in Photoshop

The History palette displays a list of each change you make to your image — every brush stroke you dab, every deletion you make, every layer you create — up to a default limit of 20 steps, or states. The list begins at the top of the History palette, and Photoshop tacks each new step on at the bottom. When you reach the limit of 20 steps, the oldest step (at the top of the list) drops off to make room for the latest one at the bottom.

If you move something repeatedly and don’t choose another tool, all the moves are considered a single step, until you do select another tool.

If your computer has lots of memory and you want to be able to move back and forth more than 20 steps, you can increase the number of steps to as many as 1,000 in the General Preferences dialog box. Choose Edit➪Preferences➪General (or Photoshop➪Preferences➪General in Mac OS X) and enter a new value in the History States box. Keep in mind that boosting this number can eat up your available memory quite quickly, because after you activate a higher number of states, Photoshop always stores up to that number every time you edit an image (even images with which you don’t contemplate needing access to more than 20 steps). A better choice may be to leave the states set to 20 and instead save snapshots of your image, as described in the following sections.