Reference Formats
PSB
Adobe's 'Large Document Format' extension of PSD for files exceeding PSD's 30,000px/2GB ceiling, supporting up to 300,000px per side, used almost exclusively inside Photoshop production pipelines.
Extension
.psb
Full name
Photoshop Big / Large Document Format
Introduced
Adobe Photoshop CS (version 8.0), 2003 — exact introduction version is not confirmed in Adobe's public documentation and is reported here based on secondary sources
Vendor
Adobe Inc.
What is inside the container
PSB extends PSD's data model unchanged — same lossless compression, same color modes, same EXIF/IPTC/XMP/ICC metadata support — while raising the maximum dimensions to 300,000 x 300,000 pixels and the file-size ceiling to roughly 4 exabytes (practically limited by disk space). It exists purely to remove PSD's size limits, not to add new features.
How to open it
For archives
Keep as master only for genuinely oversized working files (large-format print composites, VFX plates, panoramic stitches) that actually exceed PSD's 30,000px/2GB ceiling. For anything smaller, prefer PSD or a flattened TIFF derivative — PSB has even narrower tooling support than PSD, and a DAM should always also generate a downsized derivative for search and preview, since full-resolution thumbnailing of a PSB is expensive.
PSB solves a niche but real problem: some Photoshop documents — extremely large print or billboard composites, VFX matte paintings, panoramic stitches — outgrow PSD’s 30,000-pixel and 2 GB limits. Adobe’s Large Document Format lifts the ceiling to 300,000 pixels per side and roughly 4 exabytes, using the same underlying lossless data model as PSD, just without the size caps. Photoshop itself prompts users to switch to PSB automatically once a document crosses PSD’s thresholds, which is the format’s most common real-world entry point.
In a DAM, encountering a PSB file is a signal for special handling rather than routine processing. Because the same metadata model as PSD applies, EXIF/IPTC/XMP extraction works the same way — but thumbnail and preview generation is far more expensive given the pixel dimensions involved, and very few tools besides Photoshop itself can open a PSB reliably, which limits how much automated processing a DAM pipeline can safely attempt on it.
The practical DAM policy is to always generate and store a downsized derivative (TIFF or JPEG) alongside any PSB master specifically for search and preview purposes, since asking a search index or thumbnail service to open the full PSB on demand is both slow and often unsupported outside Photoshop. PSB should be treated as a specialist production format — common in print, VFX, and large-format design pipelines — rather than a general-purpose DAM asset type.
Frequently asked
When should a DAM keep PSB as the master instead of PSD?
Only for genuinely oversized working files — large-format print composites, VFX plates, panoramic stitches — that actually exceed PSD's 30,000px/2GB ceiling. For anything smaller, prefer PSD or a flattened TIFF derivative.
What are PSB's size limits?
Up to 300,000 x 300,000 pixels and roughly 4 exabytes, practically limited only by available disk space.
Does PSB add any features beyond PSD?
No — PSB extends PSD's data model unchanged, with the same lossless compression, color modes, and EXIF/IPTC/XMP/ICC metadata support. It exists purely to remove PSD's size limits, not to add new capabilities.
Can tools other than Photoshop open PSB files?
Rarely — PSB is essentially unsupported outside Photoshop, and GIMP's PSD plug-in fidelity for PSB specifically isn't well documented, so it should be tested before a DAM relies on it.
Why is PSB thumbnailing expensive in a DAM pipeline?
Given the extreme pixel dimensions PSB files can reach, full-resolution thumbnailing and preview generation are far more computationally expensive than for a standard PSD.
What's the recommended DAM policy for PSB assets?
Always generate and store a downsized TIFF or JPEG derivative alongside any PSB master for search and preview purposes, since asking a search index or thumbnail service to open the full PSB on demand is slow and often unsupported outside Photoshop.
How do files typically become PSB in the first place?
Photoshop automatically prompts users to save as PSB once a document crosses PSD's size or dimension thresholds — the format's most common real-world entry point.
What kinds of production pipelines actually generate PSB files?
Print, VFX, and large-format design pipelines producing things like billboard composites, matte paintings, or panoramic stitches — PSB is a specialist production format, not a general-purpose DAM asset type.
Sources
- PSB (Large Document Format) supports documents up to 300,000 pixels in any dimension and files up to roughly 4 exabytes, versus PSD's 30,000px/2GB limits. checked 2026-08-07 — FileInfo.com: PSB file extension
- PSB extends the PSD format with the same feature set but much higher size ceilings; exact introduction version/year is not documented in the primary source consulted. checked 2026-08-07 — Wikipedia: Adobe Photoshop
- Adobe Photoshop CS (version 8) was commercially released in October 2003. checked 2026-08-07 — Wikipedia: Adobe Photoshop version history