paint.NET is a raster image editor for changing the pixels in photographs, screenshots, icons and other bitmap files. It works with selections, layers, drawing tools, color adjustments and effects inside one image canvas. paint.NET is more capable than the basic Windows Paint workflow because layers keep separate visual elements editable. It is not a vector drawing system: resizing a small raster element still enlarges its pixels rather than rebuilding it from mathematical shapes.
Layers build the image
Each layer is a transparent pixel sheet in a stack. Opaque pixels on a higher layer cover those below, while transparent areas reveal the lower content. Text, a cutout subject and a background can therefore remain separate until export. Layer order, visibility, opacity and blend mode decide the composite result.
Only the active layer receives normal drawing and adjustment actions. Painting while the wrong layer is active can change a background instead of the intended overlay. A hidden layer stays inside a PDN project, so hiding an unwanted object is different from deleting it. Clear layer names make that distinction easier after the project has accumulated many elements.
Selections limit edits
Rectangle, ellipse, lasso and Magic Wand selections define where an operation can act. With a selection active, paint strokes, adjustments and effects stop at its boundary. This can protect the rest of the image, but a forgotten small selection can make a tool appear broken when it affects only an unnoticed region. Deselecting restores work across the active layer.
Moving selected pixels and moving the selection outline are separate actions. One changes image content; the other changes only the boundary. paint.NET also distinguishes Copy from Copy Merged. Copy reads the active layer, while Copy Merged takes the visible composite across layers.
PDN preserves editing
The native PDN format keeps layers and related project structure. PNG, JPEG and other ordinary delivery formats save a flattened result. When a layered image is saved to a format that cannot store layers, paint.NET warns or asks for flattening. Keeping a PDN master before that step preserves later access to individual elements.
JPEG adds lossy compression and cannot keep transparency. PNG retains transparency but still does not retain the editable layer stack. A flattened export is appropriate for a website or message, while the PDN belongs with the working files. Saving the only copy as JPEG can make later text correction require rebuilding the composition.
History ends on close
The History window records editing actions during the current session and lets the user jump backward or forward. Available memory and disk space limit how much history can remain. Closing the image or closing paint.NET clears that history entirely. Reopening a PDN restores layers but not the previous undo sequence.
This creates a difference between save and undo. Saving protects the current project state, while it does not create a permanent history timeline. Versioned project copies are safer for milestones that may need to return after another session.
Plugins need placement
paint.NET extends effects and file support through plugins. Effect plugins appear in effect or adjustment menus. File-type plugins add extensions to Open and Save dialogs instead of appearing as visible commands. The classic, Store and portable editions use different permitted plugin locations, and the folder names must match the documented structure.
The editor scans plugins only at startup. Copying a plugin while paint.NET remains open will not load it until the next launch. A failed plugin appears in the Plugin Errors area. The official manual warns users to obtain plugins through the paint.NET forum or links from their authors, because a plugin is executable code with access to the computer, not a harmless preset file.
