What is the PDN file format?
.pdn is a bitmap image file format used by the Windows photo-editing tool Paint.NET, developed by Rick Brewster and dotPDN LLC. Paint.NET saves projects as .pdn files by default.
The format is a .NET-serialized layered document. Modern files carry the four-byte signature PDN3 at the start, followed by a length-prefixed XML header (canvas dimensions, embedded thumbnail) and a document body that is typically Gzip-compressed.
.pdn supports image effects, transparency, multiple layers, and various bit-depth settings, making it functionally comparable to a .psd for Paint.NET users.
.pdn files can be exported into more popular image formats such as .png, .jpg or .bmp. No other major application opens .pdn natively; macOS and Linux users must convert the file first.
Security & safety
RISK: LOWA .pdn is passive image data with no scripting or macros, so it's low risk to open in Paint.NET. The only realistic caution is the source of the editor itself: download Paint.NET from the official getpaint.net site, because search results often surface paid/ad-laden 'Paint.NET' listings (including a Microsoft Store paid version by a third party) and bundled-installer mirrors. The file format carries no executable code.
Format details
in a nutshellPrograms that open PDN files
Windows1 app
Paint.NET
Free File > Open the .pdn; edit with full layers, then File > Save As to export to PNG/JPG/BMP/etc. when you need a standard image. 
macOS1 app
(no native opener - convert first)
Free Paint.NET is Windows-only. On macOS, have the file exported from Paint.NET to PNG/JPG, or run Paint.NET in a Windows VM. GIMP/Photoshop do NOT read .pdn directly. 
Linux1 app
(no native opener - convert first)
Free No Linux build of Paint.NET. Use a Windows VM/Wine, or have the file exported to PNG/JPG first; the Python 'pypdn' library can read some PDN files programmatically. Technical details
deep spec| Magic bytes | `PDN3` (0x50 0x44 0x4E 0x33) at byte offset 0 |
| XML header | Length-prefixed XML block immediately after the signature; records canvas width, height and an embedded thumbnail preview |
| Document body | .NET binary-serialized object graph; typically Gzip-compressed (0x1F 0x8B) or optionally stored uncompressed (0x00 0x01) |
| Color depth | 32 bits per pixel - 8 bits per channel (RGBA) |
| Alpha channel | Full 8-bit per-pixel alpha transparency supported on every layer |
| Layer support | Unlimited layers per document, each with independent pixel data, blend mode, opacity and visibility flag |
| Blend modes | Multiple blend modes per layer (e.g. Normal, Multiply, Screen, Overlay, Darken, Lighten, Difference) stored per-layer in the serialized document |
| Effects handling | Effects and adjustments are baked into layer pixel data; no non-destructive adjustment layers |
| MIME type | image/x-paint-net |
| Specification | No published specification; format internals inferred from Paint.NET source code and third-party analysis |
| Platform support | Native support in Paint.NET on Windows only; macOS and Linux require conversion to an interoperable format |
| Export targets | Exportable from Paint.NET to PNG, JPEG, BMP, TIFF, GIF, TGA, DDS and other formats via built-in or plugin file handlers |
| Released | 2004 (Paint.NET 1.0); current PDN3 format used by modern releases |
| Specification | www.getpaint.net |
PDN conversions
Community Q&A
asked by usersNo questions yet - be the first to ask about PDN files.
