.PSB File Extension

When a Photoshop user wants to save an image larger than 30,000 x 30,000 pixels and preserve the layer-based edits they've made to that image, they must save the image as a PSB file. The PSB file format is designed specifically to allow Photoshop users to save large Photoshop documents, whether the document is large in actual size or file size. Images larger than 2 GB in file size must also be saved as PSB files, regardless of how many pixels they contain.

PSB files contain the same types of image, text, edit, and effect layers as PSD files. In fact, the PSB file format is roughly identical to the PSD file format, except that the PSB format supports larger images. However, the PSB format is not supported by as many programs as the PSD format, which means you may have trouble opening a PSB file outside of Photoshop and other Adobe programs.

NOTE: PSB files can contain images that are up to 300,000 x 300,000 pixels in size. Photoshop does not allow users to create images larger than 300,000 x 300,000 pixels.