From The VG Resource Wiki
MS Paint with the advanced tools of Photoshop. It can be used as a beginners program for newcomers transitioning from the low features of pre-installed paint softwares to the more complex tools of later Photoshop programs.
Difference from Photoshop
- Paint.Net contains fewer features such as selection types, brush styles, stamps, and repair tools.
- When copying and pasting images or sprites containing transparent backgrounds from the web, Photoshop will provide a default background (black if pasted from the web or white if pasted from another image editing program) which could interfere with certain sprites containing similarly colored outlines, or shading. Paint.Net will at least paste images from the web with its transparency present.
- If Paint.Net is not opened through an image file, it will provide a default canvas size of 800x600 pixels. Photoshop will require creating a new file in order to display canvas options.
- Photoshop will not re-size canvas if images larger than the chosen canvas size is posted. Paint.Net will provide options on whether the canvas should be expanded to fit the exact dimensions of the image, or stay with the size given.
- When pasting images with Photoshop, it will add a new layer over the current "background". Paint.Net will paste the image on the same layer unless CTRL+SHIFT+V is pressed when pasting.
- Paint.Net has unlimited undo, while Photoshop can only hold a limited amount (appox. 19 undo).
- Pressing and holding CTRL+Z or Y will repeat the action for as long as they remain held. Pressing and holding CTRL+SHIFT/ALT+Z in Photoshop only executes the action once, requiring you to repeatedly press "Z" until the mistakes are erased or put back, or the undo limit is reached.
- Paint.Net is Window based, whereas Photoshop can be installed on Windows, Mac and Linux.
- Paint.Net is free and can be downloaded from their Official Website with unlimited use and free updates, while Photoshop only has a 30 Day trial if downloaded, after which a hard copy containing an access code must be bought with heavy updates being sold in separate discs (CS2-6), or downloaded through a subscribed account on Adobe Cloud.