The History log is disabled by default. To turn it on, go to Edit > Preferences > General (In Mac OS, Photoshop > Preferences > General). In the lower section of the dialog box, click the check box to enable History Log. You can choose whether you want the information embedded into the file as metadata, stored in a text file, or both. If you pick the text file option, you will need to click "Choose..." and tell Photoshop the name and location of the file where you want the data saved.
Under "Edit Log Items" you have three choices:
- Sessions Only - only records when Photoshop is opened and closed and when each file is opened and closed. Useful for time tracking.
- Concise - records Sessions information, plus the text that appears in the history palette.
- Detailed - records all of the above, plus the text that appears in the actions palette. This essentially tracks the complete history of editing for the file.
History data can be viewed in the metadata panel of the File Browser, or from the File Info dialog. Be careful storing the history log in the metadata--it can increase the files size and reveal editing details that you'd prefer to remain undisclosed.

