PSD and PSB in one paragraph
The two formats store the same things: layers, masks, effects, text. PSB simply raises the ceilings. A PSD stops at 2 GB and 30,000 × 30,000 pixels; a PSB goes up to 300,000 pixels per side and has no practical size cap. Photoshop switches to PSB for panoramas, print banners, high-resolution composites and documents with hundreds of layers.
Opening one
- Open the editor on a desktop computer.
- Drag the .psb in, or use File › Open.
- Wait. A multi-gigabyte file takes a while to read, and the tab may look idle while it works.
Will my computer cope?
Memory is the constraint. A PSB is unpacked into your browser's memory, and a browser tab gets only part of what the machine has. Before opening a big one:
- close other tabs and applications;
- use a desktop or laptop with 16 GB of RAM or more for files over a gigabyte;
- if the tab crashes, the document is beyond what a browser can hold on that machine.
For files that large, the native PhotoCraft desktop app isn't bound by browser limits and is the better tool.
Making it smaller
Often the goal is to get something manageable out of a PSB:
- A flat copy. File › Export › Export As writes a JPEG or PNG of the whole canvas.
- Lower resolution. Image › Image Size scales the document down. A print banner rarely needs every pixel for an on-screen proof.
- Fewer layers. Delete hidden layers and merge groups you won't edit again, then save. Once the document fits within PSD's limits it is written as an ordinary PSD.