The short answer
What file type is PSD?
PSD stands for Photoshop Document. It is the native save format of Adobe Photoshop, and it is a layered raster document rather than a delivery image. Saving as .psd preserves every layer, mask, blend mode and channel losslessly, so the document can be reopened later and edited as if you never closed it.
That one distinction explains nearly everything else about the format. A JPG is the print. A PSD is the negative, the darkroom notes and the enlarger settings, all in one file. Once you see the PSD file type as a saved workspace instead of a saved picture, its strengths (endless re-editing) and its weaknesses (size, portability, no browser support) both stop being surprising.
If you have simply been sent one of these files and want the plain-language version first, start with what a PSD file is and come back here for the format detail.
Why the PSD file type has layers when JPG and PNG do not
JPG, PNG and WebP are interchange formats. Their job is to encode one final grid of pixels as compactly as possible and hand it to a decoder — a browser, a phone, a printer driver — that must render it identically everywhere. A single flat raster is exactly the right design for that job, and it is why every device on earth can open a JPG.
The PSD file type was designed for the opposite job. It serialises the state of an editor. Photoshop’s editing model is a stack of layers composited from the bottom up, so the format that saves a Photoshop session has to record that stack: each layer’s pixels, position, opacity, blend mode, name and visibility, plus the masks and adjustments that modify them. Layers are not a bonus feature bolted onto the format — they are the thing being saved.
This is also why adding layers to PNG was never realistic. Every browser would then have to agree on how to composite dozens of blend modes, clipping masks and adjustment layers before showing a single image, and disagreement would mean the same file looks different in different places. Delivery formats deliberately give that power up. Document formats deliberately keep it.
The practical rule
Edit in a layered document, deliver in a flat format. Keep the PSD as your master and export PNG or JPG copies for anything that has to be viewed, uploaded or sent to someone who will not be editing it.
What a .psd file actually stores
Adobe publishes the specification for the PSD file type, which is why non-Adobe software can read these documents at all. Open one up and you will typically find:
- Layers and layer groups — Independent images stacked in order, each with its own name, opacity, blend mode and visibility toggle, optionally nested into folders.
- Layer masks and clipping masks — Greyscale masks that hide parts of a layer without deleting them, so a cut-out can be refined again and again with nothing lost.
- Adjustment layers — Curves, levels, hue/saturation and similar corrections stored as instructions applied to the layers below, not baked into them.
- Smart objects — Embedded or linked source content that can be scaled and re-edited without degrading the original pixels. Mockup templates are built on these.
- Live text layers — Editable type with its font, size and tracking, which is why a headline in a PSD can be rewritten instead of retyped and rebuilt.
- Vector shapes and paths — Resolution-independent shapes, paths and clipping paths stored alongside the raster layers.
- Channels and colour data — The colour mode (RGB, CMYK, greyscale, Lab and others), the bit depth, alpha channels, spot colour channels and the embedded colour profile.
- A flattened composite — A pre-rendered preview of the finished stack. This is what lets some viewers show a thumbnail of a file they cannot truly edit — and why Photoshop’s "Maximize Compatibility" option matters when you share files.
All of that is stored without lossy compression. The PSD file type uses lossless schemes (run-length encoding by default, ZIP as an option), so re-saving a document ten times does not degrade it the way re-saving a JPG ten times does.
PSD file type vs PNG, TIFF and JPG
The honest comparison is not "which format is best" but "which stage of the work is this file for".
| Format | Layers | Transparency | Compression | Made for |
|---|---|---|---|---|
| PSD | Yes — the full editing stack | Yes, per layer | Lossless (RLE or ZIP) | Working documents and design handoff |
| TIFF | Photoshop layers only, via a private tag | Yes | Lossless or none | Print masters and long-term archives |
| PNG | No | Yes, full alpha channel | Lossless | Web and app delivery with transparency |
| JPG | No | No | Lossy | Photographs delivered at small file sizes |
TIFF can carry Photoshop layers, but they are written into a private tag that most other TIFF readers ignore — open that same file in another application and you usually get the flattened composite only. Treat layered TIFF as a Photoshop convenience, not a portable guarantee.
So a designer keeps the master as a PSD, sends a PNG when the client needs a logo with a transparent background, sends a JPG when the client needs a photo in an email, and sends a TIFF when a printer asks for one. Those are four answers to four different questions, not four competitors.
Who actually uses this format, and for what
Photographers and retouchers
Non-destructive retouching lives or dies on masks and adjustment layers. A retoucher keeps the layered document so a client note three weeks later means moving a slider, not redoing the edit.
Print and packaging designers
CMYK colour, spot channels, 16-bit depth and embedded profiles are supported here and absent from PNG and JPG, which makes the format a practical pre-press working file.
Agencies and marketing teams
Banner sets, social variants and device mockups ship as layered templates so the next person can swap the product shot, change the headline and re-export in minutes.
Game, film and 3D artists
Texture sheets, matte paintings, UI kits and sprite sheets are authored in layers and flattened only at export, keeping every element independently adjustable.
One group has largely moved on: interface designers. Screen design shifted to vector-first tools, and the PSD file type is now rare for new UI work. Everywhere that pixels, masks and print colour matter, it is very much still standard.
Real limits of the PSD file type
A file format built to preserve everything pays for it. The limits below are the ones that actually interrupt work:
- Size — Every layer stores its own pixels losslessly, so a document that exports to a 2 MB JPG can easily be 300 MB on disk. The format also caps out at 30,000 pixels per side and 2 GB per file; beyond that Photoshop uses the large-document sibling, .psb.
- Nothing on the web displays it — No browser renders the PSD file type natively. It cannot be an <img> source, a social preview or an email attachment people can simply click and view.
- Fidelity drifts between applications — Other editors read the published spec, but support is uneven. Live text is commonly rasterised on import, and layer styles, adjustment layers and smart objects may be approximated or flattened. Vector text stays truly editable mainly inside Adobe software.
- Fonts are references, not contents — A text layer points at a font by name. Open the document on a machine without that font and the type is substituted, which quietly changes the layout.
- Newer features degrade on older versions — Features added in recent releases may not survive a round trip through an older one, and a file saved without a flattened composite can refuse to preview anywhere else at all.
None of that makes the PSD file type a poor choice — it makes it a poor delivery format. Keep the document as the master, and hand out flat exports.