What Is a PSD File? Photoshop Document, the Working File Behind the Picture
PSD stands for Photoshop Document. It keeps every layer separate so the work can be changed later. Jump to your question below, or read it through in order.
PSD stands for Photoshop Document. It keeps every layer separate so the work can be changed later. Jump to your question below, or read it through in order.
PSD stands for Photoshop Document. It is Photoshop's native file format, the working file Adobe Photoshop saves. It keeps every layer, mask, adjustment and effect separate rather than baking them into one picture.
That is the point of it. A JPEG is the photograph. A PSD is everything that went into making the photograph, still taken apart.
Think of two things on a designer's desk. One is a printed poster. Next to it, a folder of cut-out pieces, tracing paper and pencil notes that made it.
PSD files are that second thing. Move a headline, change a sky, turn one element off. Nothing else on that PSD has to be rebuilt.
Everything else on this page follows from that. PSD files are large because they keep those pieces. They are awkward to share because most software only sees a finished poster.
.psdimage/vnd.adobe.photoshop8BPS, hex 38 42 50 53.psb, the Large Document FormatRename your PSD to holiday.jpg and Photoshop still opens it. Rename a JPEG to artwork.psd and Photoshop still knows better.
Software reads the first four bytes, and in every Photoshop Document those bytes spell 8BPS. Adobe's published specification is blunt about it.
“Signature: always equal to ‘8BPS’. Do not try to read the file if the signature does not match this value.”
Useful when a PSD refuses to open. Two minutes in a text editor tells you whether you have a damaged Photoshop Document or something that was never one.
Adobe publishes the format, which is rarer than people assume for a proprietary file. Anybody can write software that reads or writes PSD files, and that is exactly why free tools manage it.
Adobe adds a caveat worth respecting. That document explains how to read bytes, not what they mean, so third-party support always trails Photoshop itself.
Layers, masks, adjustment layers, Smart Objects, paths and layer styles. Six kinds of thing a flat image throws away and a Photoshop Document keeps, ready to change.
Save that same artwork as PNG and you get one grid of pixels. Every decision behind it is gone. Save it as PSD and multiple layers stay separate, with every decision still editable.
Channels sit alongside all of that. One per color. Alpha channels hold saved selections, and spot channels carry inks a printer mixes specially.
This is what people mean by non-destructive editing. Nothing in the list above changes the original pixels. Turn every adjustment off and the photograph you started with is still underneath, untouched.
It is also why PSD files get so large. Keeping your options open costs storage.
Two ceilings. No side may pass 30,000 pixels, and a saved PSD may not pass 2 GB. Hit that second one and Photoshop refuses to save at all.
Most people meet these in one way. Hours into a job, saving fails. Photoshop gives no hint that any limit existed.
| Limit | Value | When you meet it |
|---|---|---|
| Canvas size | Up to 30,000 pixels on either side | Billboards, long banners, gigapixel panoramas |
| File size | 2 GB saved on disk | Retouching jobs, deep layer stacks, many Smart Objects |
Canvas size is rarely a problem. 2 GB is, and it does not take an unusual project to get there. One 16-bit poster with forty layers manages it comfortably.
Photoshop says: could not save because the document exceeds the 2.00G limit for saving Photoshop files. Nothing is damaged and nothing is lost. It simply will not write a PSD that large.
Do not close it. Do not flatten it in a panic. Save As, then Large Document Format. That same PSD saves without losing a single layer.
Worth knowing before it happens, because instinct in that moment says delete layers. Section 4 is a better answer, and section 7 covers what made your PSD so big in the first place.
PSB is the Large Document Format. Same format as PSD, one byte changed. It raises your ceiling from 30,000 pixels to 300,000 and from 2 GB to roughly 4 exabytes.
This is the most useful thing on this page and almost nobody mentions it. PSB is not a different kind of file. It is your PSD with wider numbers in its header.
| PSD | PSB | |
|---|---|---|
| Full name | Photoshop Document | Large Document Format |
| Version byte | 1 | 2 |
| Maximum side | 30,000 px | 300,000 px |
| Maximum file | 2 GB | About 4 exabytes |
| Layers and masks | Yes | Yes, identical |
| Read by other tools | Widely | Less widely |
Both files start with those same four characters, 8BPS. One byte after them says 1 or 2, and that single digit moves your ceiling.
Adobe introduced the Large Document Format with Photoshop CS in 2003. Anything released since opens one.
Use this when Photoshop refuses to save and says the document exceeds the 2.00G limit.
Only switch when you need to. PSB costs you reach. Some software that happily reads PSD stops at PSB, and a client who cannot open what you sent will not care which byte is different.
If your job fits under both ceilings, stay on PSD.
Maximize Compatibility stores a flattened copy of your finished image inside the PSD. That copy is all most other software can display, and it is why one PSD can be twice the size.
Photoshop asks about this at save time and most people click past it. What it decides is whether your PSD makes any sense to software that is not Photoshop.
With it on, Photoshop saves your layers and one flattened picture of the finished result, tucked into that same PSD. Two copies of your artwork, one editable and one not.
With it off, only layers go in. Photoshop is happy. Almost nothing else is.
| What you noticed | Why |
|---|---|
| The PSD opens flattened in other software | That software is showing a composite. It never had access to layers |
| The PSD suddenly doubled in size | A composite is a second copy of your image, saved alongside your layers |
| Nothing shows a preview or thumbnail | With that setting off there is no composite to preview. See section 9 |
Lightroom Classic will not import a PSD saved without it. If photographs edited in Photoshop keep failing to appear back in your catalogue, this is usually why. Your PSD is fine.
Most asset managers and preview tools behave that way too. They read a composite or they read nothing.
So that trade is plain. Off means smaller PSD files that only Photoshop understands. On means larger ones everybody can at least look at.
Photoshop, obviously. Also Photopea in any browser, GIMP, Krita, Affinity Photo, Paint.NET and Preview on macOS. Most of them read the layers; the rest show the flattened composite.
Adobe publishes the format, so anybody may write software that reads it. That is why how to open a PSD has so many answers, and why the list below is as long as it is.
Here is the catch. Reading the layers and reading the picture are different jobs, and plenty of tools only manage the second.
Anything showing you a flat image is reading the composite that Maximize Compatibility put there. Turn that setting off and those same tools show nothing at all.
Sent a PSD by somebody who assumed you had Photoshop? Open Photopea in a browser tab and drag the PSD in. No account, no install. Layers are there.
For a one-off look at what the image is, Preview on a Mac or any of the free desktop editors will do.
Layers are the main cost, because every layer keeps its own pixels. Smart Objects carry complete files inside them, and Maximize Compatibility adds a flattened copy on top of everything else.
A photograph that is 4 MB as JPEG can be 900 MB as PSD. Nothing has gone wrong. The two are storing completely different things.
Use this when your PSD will not fit in a share link, or the 2 GB save has started failing.
PSD compression is lossless, so none of this costs image quality. Photoshop packs the data with RLE or ZIP, and both put back exactly what went in. Saving the same PSD twenty times leaves it identical.
What you are trimming is options, not pixels. Every layer you merge is a decision you can no longer undo.
Keep working in PSD, then export. TIFF is one other format that holds layers. PNG and JPEG hold none, which is exactly why they are what you send.
These are not competing formats. They sit at different points in one job, and confusion comes from handing over the wrong one at the wrong moment.
| Format | Keeps layers | Lossless | Use it for |
|---|---|---|---|
| PSD | Yes, plus masks and effects | Yes | The work in progress, and the archive copy |
| TIFF | Yes, though support varies | Yes | Print handover, and long-term storage |
| PNG | No | Yes | Web graphics that need transparency |
| JPEG | No | No | Photographs going out to the world |
TIFF surprises people. It can carry layers, and it is more widely readable than PSD, which makes it a safer archive format when files have to outlive whatever made them.
Photoshop also exports straight to the PDF file format, which keeps vector text sharp and suits anything that will be printed or read rather than edited.
It is your only copy with the decisions still in it. Delete it and you have a poster but not the pieces, and your next revision starts from scratch.
Nobody outside your project needs those layers. Export PNG or JPEG for web, TIFF or PDF for print. Keep the PSD.
Designers working in vectors face this split too. An Adobe Illustrator artwork file plays the part PSD plays here, and EPS graphics or PDF is what goes out.
Windows ships no PSD thumbnail handler, so a blank icon means nothing is wrong with your PSD. Adobe Bridge shows them. Never install a DLL from a download site to fix this.
File Explorer previews JPEG, PNG and plenty of video. Open a folder of Photoshop Documents and you get a row of identical blank icons.
That is Windows working as designed. It has never carried code that reads Photoshop Documents, and Microsoft's own support threads say the same thing.
One fix circulates everywhere and you should not follow it. It tells you to download a file called psicon.dll, copy it into a system folder, then download and run a .reg file. This page carried that advice for years, and it has been removed.
That is an unsigned library from an unnamed source plus a registry merge nobody has read. Even when it works, you have no idea what else went in with it.
Rule of thumb. A thumbnail is worth almost nothing. It is never worth running code from a download site on the machine holding your work.
macOS behaves differently. Finder and Preview both read PSD files already, because the composite is enough for them to render. Same PSD, same setting, different operating system.
Most PSD files that will not open were copied or downloaded incompletely. Check the first four characters read 8BPS and compare its size against the source before reaching for anything else.
Photoshop is vague here on purpose. Could not complete your request because the file is not compatible covers half a dozen unrelated faults.
People call these corrupt PSD files. Often nothing is corrupt at all. Bytes are missing, and Photoshop has no polite way to say so.
| What you see | What it usually means | Start with |
|---|---|---|
| Not a valid Photoshop document | Truncated, or it was never a PSD | Check for 8BPS |
| Opens, but the layers are gone | You are looking at the flattened composite | Open it in Photoshop or Photopea |
| Opens blank or white | Layer visibility, or a mask hiding everything | The Layers panel |
| Older Photoshop refuses it | Saved with a newer feature, or saved as PSB | Ask for a PSD re-save |
| Colors look wrong everywhere else | CMYK or Lab, being shown by something expecting RGB | Convert on export |
The first three steps are free and settle most cases. Repair software belongs at the bottom, and it is worth understanding what it can and cannot give back.
8BPS at the very start. Anything else and this was never a Photoshop Document..psd will not open in older software.No repair tool can recover bytes that never reached your computer. Pages advertising recovery for an interrupted download are scanning the part you already have.
Work out whether your PSD is incomplete or merely unreadable before paying for anything. Step 2 answers that in ten seconds.
One habit prevents most of this. Keep the PSD somewhere backed up, and treat the exported JPEG as disposable rather than the other way round.
Five sections in fixed order, starting with 8BPS and a version byte. Eight color modes, four bit depths and lossless compression. Adobe publishes the lot.
You do not need this section to fix anything. It is here because two details explain behavior that otherwise looks arbitrary.
Adobe's specification lays them out in this order, and every Photoshop Document follows it.
8BPS, then the version byte, channel count, height, width, bit depth and color mode. Twenty-six bytes that describe the whole document.Section five is the practical one. Maximize Compatibility governs what lands there, which is why one checkbox decides whether Preview, Bridge and File Explorer can show your artwork.
The first twenty-six bytes describe the entire document. Six of them settle the two questions people actually ask. Is this really a PSD, and is it PSD or PSB?
Any text editor shows you the signature. A hex editor shows the rest, and the version byte right after it is the one that separates the two formats.
| Field | Values |
|---|---|
| Color mode | Bitmap, Grayscale, Indexed, RGB, CMYK, Multichannel, Duotone, Lab |
| Bit depth | 1, 8, 16 or 32 bits per channel |
| Compression | Raw, RLE, ZIP without prediction, ZIP with prediction |
| Version byte | 1 for PSD, 2 for PSB |
| Dimensions | 1 to 30,000 for PSD, 1 to 300,000 for PSB |
Note what is missing from that compression list. There is no lossy option, which is why a PSD never degrades however often you save it.
Compare that with PDF files, which can carry JPEG-compressed images inside them, so a page recompressed repeatedly does lose quality.
PSD is Adobe's and always has been. Adobe also publishes how to read it, which is an unusual combination and the reason free software handles PSD files at all.
The catch is in Adobe's own wording: the document explains how to read the bytes, not how to interpret them. So third-party tools track Photoshop's newer features slowly, and layer styles are usually the first thing to go.
Two questions sort out most of what is left. Answer them in order.
Check for 8BPS and compare its size. Anything that arrived short stopped mid-copy, and section 10 says what that leaves behind.
Open it in Photopea. If layers appear there, whatever you tried first was only reading a composite. Section 5 explains why.
Working across the Adobe set? Illustrator AI artwork is this file's vector equivalent, and the Portable Document Format is what usually leaves the studio.
Handing work to a printer? EPS encapsulated PostScript and plain PostScript files still turn up in prepress, and CorelDRAW CDR drawings cover another studio in the building.
Chasing an older raster format instead? We cover Truevision TGA images, PCX picture files and DDS texture files as well.
New to all of this? What a file format is covers the ground underneath, and our file format guides list the rest.
Found something here that does not match your version? Send us the exact wording on screen and we will check it against Adobe's specification.