The .psb format (Photoshop Big) is Adobe Photoshop's solution for files exceeding Photoshop Document's (.psd) 2GB size limit. Unlike .psd, .psb files can store huge documents (up to 4.6 million terabytes theoretically). Opening them functions similarly to standard Photoshop files but requires software capable of reading this specific large-document format. It preserves layers, effects, and high-resolution data otherwise too large for a .psd.

To open a .psb file, you primarily need Adobe Photoshop. Current versions readily open .psb files. Some alternative image editors, like Affinity Photo, also support importing .psb files, though compatibility might not be 100% for all layer features. This is vital in industries handling massive assets like high-resolution photography, detailed print materials, complex digital paintings, or large-scale panoramas created directly within Photoshop.

The main advantage is reliably working with colossal files directly in Photoshop. A key limitation is that many non-Adobe applications (including older Photoshop versions before CS) cannot open .psb files at all, restricting editing options. File compatibility remains crucial when sharing; recipients without supporting software will face barriers. Cloud-based workflows might emerge as solutions, but native .psb support outside Adobe's ecosystem remains limited.