Default File Format for Save As in Paint.NET

When you click "Save As" in Paint.NET, the default suggested file format is the native .pdn (Paint.NET Document) format. This article explains how Paint.NET determines its default save format, why the application prioritizes .pdn, and how the program behaves when dealing with different image conditions like multiple layers or pre-existing files.

The Native .pdn Format

For any new, untitled canvas created from scratch, Paint.NET automatically sets the file type in the "Save As" dialog to .pdn.

The .pdn format is proprietary to Paint.NET and is designed to preserve project-specific data that standard formats cannot hold. This includes:

  • Multiple separate image layers
  • Layer visibility and opacity settings
  • Layer blend modes

How Image Layers Affect the Default Format

Paint.NET dynamically adjusts its save recommendation based on the composition of your project:

  1. Multi-Layer Projects: If your project contains two or more layers, Paint.NET will always suggest .pdn as the default format. This safety mechanism prevents you from accidentally flattening your work and losing individual layers.
  2. Existing Single-Layer Images: If you open an existing file (such as a .png or .jpg) and leave it as a single layer, clicking "Save As" will default to that file's original format rather than .pdn.
  3. Modified Existing Images: If you open a standard image like a .jpg and add a second layer, the default "Save As" behavior will immediately switch to .pdn to protect the new layer structure.

Exporting to Standard Formats

While .pdn is the default for new or layered work, it is not viewable by standard web browsers or most external photo viewers. To save a project for sharing or online use:

  1. Click File > Save As.
  2. Click the Save as type dropdown menu beneath the file name.
  3. Select a standard format such as PNG, JPEG, or BMP.
  4. If your project contains multiple layers, Paint.NET will prompt you to Flatten the image before saving the export.