Reduce large PSB file size

Working with large Photoshop documents? PSB files easily reach gigabytes, and metadata bloat makes it worse. This page covers what is safe to remove and how multi-gigabyte files are handled.

Updated · Free · No upload · Keeps every layer

PSB (Photoshop Big) was designed for documents Photoshop cannot fit into a regular PSD: billboard art, large matte paintings, multi-gigapixel scans, game environment sheets. Just like PSD, PSB files accumulate unnecessary XMP metadata over time. The difference is scale. With files this big, even a few hundred megabytes of bloat is a real cost in upload time, backup storage and the time Photoshop takes to open and save.

There is no size limit in the browser: the file is streamed from disk and the result is written to disk, so 3 to 5 GB PSBs process in seconds. The command-line route below is for whole folders.

What this tool does for PSB

  • Strips DocumentAncestors and its RDF wrappers from the document’s XMP
  • Descends into embedded smart objects and strips the same field there
  • Preserves all layers, masks, smart objects and 64-bit section lengths
  • Output opens identically in Photoshop
  • Same processing path as PSD, no special handling needed
Drop your PSD here or click to choose · .psd / .psb

Where the bytes go in a big PSB

Large documents have three typical bloat sources, and they stack:

  1. Ancestor metadata multiplied by smart objects. Environment and matte files are built by placing dozens of assets. Each placed asset becomes an embedded smart object with its own XMP packet, and each packet carries the full ancestor list. This is the part the tool removes.
  2. Embedded originals. A placed 200 MB RAW or layered PSD is stored whole inside the PSB even if it is scaled down to a corner. Linking instead of embedding, or rasterizing final elements, removes this.
  3. The composite preview. With Maximize Compatibility on, Photoshop stores a flattened copy of the whole canvas. At 20,000 × 20,000 pixels in 16-bit that alone is 2.4 GB before compression. Turn it off for working files.

Disk, not memory. The engine reads the PSB in 8 MB chunks and writes the result to the browser’s private storage on disk, so memory use stays around a few megabytes regardless of file size. Use a normal window rather than private browsing for files over 2 GB, since private windows keep that storage in memory.

For whole folders: the command line

The engine behind this page is the open-source psd_ockham utility. It runs on macOS, Windows and Linux and is the right choice when you have a directory of files rather than one. Usage: 

psd_ockham huge-matte.psb            # writes huge-matte_cut.psb next to it
psd_ockham huge-matte.psb clean.psb  # or choose the output name

Point it at a folder in a shell loop and it will clean an entire project archive unattended. Because output is deterministic, running it a second time changes nothing.

Working habits that keep PSBs small

  • Clean the master once with this tool, then work from the cleaned copy.
  • Link large placed assets rather than embedding them.
  • Keep Maximize Compatibility off until final delivery.
  • Stay in 8-bit unless the grading pipeline needs 16.
  • Re-run the cleaner before archiving or handing off.

Real numbers: before and after

The first row is a file we measured with this exact engine. It took 1.4 seconds on a laptop. The other rows are cases reported by Photoshop users on Adobe’s forums after removing the same metadata field.

File Before After Saved
Game art, 1920×1080, RGB 8-bit, many smart objects 902 MB 254 MB 71.8%
Retouched photo passed between editors (Adobe Community) 65 MB 110 KB 99.8%
Reused PSD template, images placed repeatedly (Adobe Community) 100 MB 7 MB 93%

Your result depends entirely on how much ancestor history the file carries. A PSD created in one sitting and saved once may shrink by only a few kilobytes. A file that has been a template for two years can lose most of its size.

Step by step

  1. Open the tool. Open psd.imtool.app in any modern desktop browser. Nothing to install.
  2. Drop the file. Drag the .psd or .psb file onto the drop zone, or click it to pick a file. The file stays on your device.
  3. Wait a few seconds. The engine reads the file in a Web Worker and removes the DocumentAncestors metadata from the main document and every embedded smart object.
  4. Download. Compare the before and after sizes, then download the cleaned copy. The original is untouched.

FAQ

Why is my PSB so much bigger than my PSD?

PSB (Large Document Format) supports documents larger than 30,000 × 30,000 pixels and over 2 GB. The format itself is the same as PSD with 64-bit lengths. The bloat sources are the same too: accumulated XMP metadata and embedded smart objects.

What is the file size limit for the browser version?

There is no fixed limit. The engine streams the file from disk in 8 MB chunks and writes the result to the browser’s private storage rather than memory, so 3 to 5 GB PSBs process in seconds. You need free disk space roughly equal to the output size. Private/incognito windows keep that storage in memory and cap it near 2 GB, so use a normal window for very large files.

Which browsers handle multi-gigabyte files?

Chrome, Edge, Firefox 111+ and Safari 16.4+ all support the on-disk storage the tool uses. Older browsers fall back to keeping the output in memory, which works up to roughly 1.5 GB.

Can I batch-process many PSBs?

Not in the browser; the UI processes one file at a time. The command-line version takes a folder.

Should I convert a PSB back to PSD to make it smaller?

No. The container adds only a few bytes of larger length fields. If the document fits PSD limits, converting changes nothing meaningful. Size comes from content and metadata, not the extension.