What is the PSD file format?
The .psd file type stands for Adobe Photoshop Document. .psd is one of the most widely used file formats in graphics and digital design today. Most graphic designers create their work in Adobe Photoshop, which saves projects natively as .psd documents. .psd files are also used widely by web designers and developers to implement layouts and convert them into HTML and CSS.
What sets .psd apart is its support for a fully layered structure, making it uniquely powerful for designers - each layer, text block, shape, and adjustment remains independently editable after saving. Layers can be pixel-based, vector-based, text, fill, adjustment, or smart objects, enabling non-destructive editing workflows that flat formats such as .jpg or .png cannot offer.
.psd is a proprietary binary format owned by Adobe Inc., identified by the four-byte file signature 8BPS at byte offset 0. The format supports bit depths of 1, 8, 16, and 32 bits per channel, and color modes including RGB, CMYK, Grayscale, Lab, and Multichannel. Maximum image dimensions are 30,000 × 30,000 pixels with a 2 GB file size cap; projects exceeding those limits should use the companion .psb (Large Document) format instead.
While Adobe Photoshop is the native application, .psd files can also be opened in GIMP, Affinity Photo, Krita, and the browser-based editor Photopea, though third-party support for advanced features - such as smart filters, adjustment layers, and layer effects - varies by application.
Security & safety
RISK: LOWPSD is an image/document format, not executable, so a PSD on its own won't run code. Two real cautions: (1) PSDs can be huge, and malformed/corrupt ones occasionally crash older viewers - open untrusted files in a sandboxed or web tool (Photopea) if unsure; (2) avoid sketchy 'free PSD viewer/converter' download sites, which often bundle adware/PUPs - prefer GIMP, Krita or Photopea. There have historically been parser vulnerabilities in image libraries, so keep your editor updated.
Format details
in a nutshellPrograms that open PSD files
Windows6 apps
Adobe Photoshop
Paid Open the PSD directly - full layer, text and smart-object editing (Creative Cloud subscription). 
GIMP
Open-source File > Open the .psd; layers import (some adjustment layers/effects rasterize or are dropped). 
Photopea
Freemium Free browser editor: drag the PSD in; opens with layers intact, then export to PSD/JPG/PNG. 
XnView MP
Freemium Fast viewing/batch-converting PSDs (uses the embedded composite preview; not for editing layers). 
macOS5 apps
Linux3 apps
Photopea
Freemium Full PSD editor in the browser; opens and saves PSD with layers, exports to JPG/PNG/etc. Technical details
deep spec| File signature (magic bytes) | `8BPS` (hex `38 42 50 53`) at byte offset 0 |
| Version field | 2 bytes after signature: `0x0001` = PSD, `0x0002` = PSB (Large Document) |
| Maximum image dimensions | 30,000 × 30,000 pixels |
| Maximum file size | 2 GB |
| Bit depth | 1, 8, 16, and 32 bits per channel |
| Color modes | Bitmap, Grayscale, Indexed, RGB, CMYK, Lab, Duotone, Multichannel |
| Maximum channels | Up to 56 channels (including alpha and spot color channels) |
| Layer types | Pixel, text, shape, adjustment, fill, and smart object layers |
| MIME type | `image/vnd.adobe.photoshop` |
| Compression methods | None (raw), PackBits RLE, ZIP without prediction, ZIP with prediction |
| Byte order | Big-endian |
| File structure | Five sections: File Header, Color Mode Data, Image Resources, Layer and Mask Information, Image Data |
| ICC profile support | Embedded in the Image Resources section |
| Transparency | Per-layer transparency masks and alpha channels |
| Smart Objects | Embeds raster, vector, or raw files as non-destructive editable layers |
| Large-document variant | `.psb` supports up to 300,000 × 300,000 px and files larger than 2 GB |
| Released | 1990 (Adobe Photoshop 1.0) |
| Specification | www.adobe.com |
PSD conversions
Community Q&A
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