.PSD File Extension

The PSD format is a fully editable, uncompressed format, ideal for editing raster images. You can modify individual elements within a PSD file, such as images, shapes, text, and effects. New versions of Photoshop (2024 and later) allow you to create and insert AI-generated graphics.

PSD files support RGB, CMYK, grayscale, monochrome, duotone, indexed color, Lab color, and multichannel color modes.  You can change the color mode by selecting the Image → Mode in Photoshop.

The data structure of a PSD file

The Photoshop file format is comprised of five sections:

1. File Header - Stores image properties like dimensions, bit depth, color mode, and channel count
2. Color Mode Data – Includes additional data if the file uses indexed or duotone colors
3. Image Resources – Contains non-image elements such as guides, text styles, or paths
4. Layer and Mask Information – Stores data about layers, masks, blending modes, and effects
5. Image Data – Contains the actual image data (pixel data) and the compression method used to reduce the overall file size (e.g., raw, RLE, ZIP)

NOTE: Photoshop supports PSD files up to 30,000 x 30,000 pixels or 2 GB in size. Images larger than these limits must be saved in the .PSB (Photoshop Big) Large Document format.