PSB is a file extension for an image file used by Adobe Photoshop. PSB files are a large document format similar to a PSD file but for a larger image size.
The Large Document Format (8BPB/PSB) supports documents up to 300,000 pixels in any dimension. All Photoshop features, such as layers, effects, and filters, are supported by the PSB format. The PSB format is identical to the Photoshop native format in many ways.
PSB (Large Document Format)
PSB is a file extension for an image file used by Adobe Photoshop. PSB files are a large document format similar to a PSD file but for a larger image size.
The Large Document Format (8BPB/PSB) supports documents up to 300,000 pixels in any dimension. All Photoshop features, such as layers, effects, and filters, are supported by the PSB format. The PSB format is identical to the Photoshop native format in many ways.
Identification
The file header contains the basic properties of the image.
Source: https://www.adobe.com/devnet-apps/photoshop/fileformatashtml/#50577409_pgfId-1057388