Paint.NET is free image editing and photo manipulation software designed to be used on computers that run Windows. It supports layers, unlimited undo, special effects, and a wide variety of useful and powerful tools.

It started development as an undergraduate college senior design project mentored by Microsoft, and is currently being maintained by some of the alumni that originally worked on it. Originally intended as a free replacement for the MS Paint software that comes with Windows, it has grown into a powerful yet simple tool for photo and image editing.

The programming language used to create Paint.NET is C#, with a small amount of C++ for installation and shell-integration related functionality.

This update enhances the Line/Curve tool, significantly reduces the download size, and fixes some bugs related to opening and saving files in Windows Vista.
New: Line/Curve tool has been enhanced to allow drawing arrowheads, and to draw with various dashed- and dotted- styles.
New: Image tab thumbnails now have an indicator if the respective image has unsaved changes (an orange asterisk is shown).
Improved: The Save Configuration dialog (choose JPEG quality, etc.) now allows you to maximize it. It also remembers its relative location and size.
Changed: The help file / documentation is now hosted online. This has reduced the download size by more than 3 MB, and will also allow us to provide translations without ballooning the size of the download (each language would have added between 2 and 4MB).
Changed: The "image list button" (downward triangle) is also shown when only 1 image is open (it used to only display if 2 or more images were open). This is being done for the sake of consistency.
Fixed: Some operations would reset the selected layer to the first/lowest layer. This selection is now preserved.
Fixed: The Image->Rotate commands no longer hangs if a selection was active.
Fixed: Several problems have been fixed with our implementation surrounding the new Vista Open/Save dialogs. This includes: opening an image from an http:// source, opening images from a digital camera that is not mapped to a file system path (such as a drive letter), the Save dialog not always prompting you about overwriting an existing file, and many corner cases that previously caused crashes.