PSD viewer: open Photoshop files without Photoshop

What it shows

• The flattened image Photoshop saved inside the file, drawn on a canvas that holds every pixel and scaled down to fit your screen. Because it is Photoshop's own merged picture, effects, adjustments and smart objects look exactly as they did in Photoshop.
• Document facts from the file header: width and height in pixels, colour mode (RGB, Grayscale, Indexed, Bitmap, CMYK, Lab…), bits per channel (8, 16 or 32), channel count, and whether it is a normal PSD or a large-document PSB.
• The layer tree, top of the stack first as in Photoshop's Layers panel: groups with their layers nested inside, each layer's name, whether it is hidden, its opacity, and tags for text, adjustment, smart-object, clipped, masked and effect layers and non-normal blend modes.
• One layer's pixels when you click it, cropped to that layer's own bounds, on a checkerboard so transparency shows.
• Save as PNG for the flattened image and for the selected layer. The PNG is made in this tab and saved by your browser's normal download, at full resolution.

What it cannot do

• Files saved without “Maximize compatibility”. Photoshop then stores no real flattened image, only a blank placeholder, and the page says so instead of showing a white rectangle. The layers are still listed and each one's pixels still open. Re-saving from Photoshop with the option ticked (it is under Preferences › File Handling, and asked on save) fixes it.
• Re-rendering what Photoshop computes live. Adjustment layers (curves, levels, hue/saturation…) are settings, not pixels, and are not re-applied. Layer effects (drop shadow, stroke, glow) are not drawn onto a single layer's view. A smart object shows the preview pixels Photoshop stored, not the embedded original. None of this affects the flattened image, which already contains them.
• CMYK, Lab, Duotone and Multichannel documents. The reader decodes RGB, Grayscale, Indexed and Bitmap only. For the others the page shows the header facts and says it cannot go further; Photoshop's Image › Mode › RGB Color converts them.
• Very large files. The whole file is read into this tab's memory, and the flattened image needs 4 bytes per pixel on top: a 12,000 × 8,000 px document is 384 MB as a canvas. Big PSB files can run a tab out of memory, and phones hit the limit much sooner than desktops. Browsers also cap canvas size (for example about 268 million pixels in Chrome, less in Safari on iPhone), so the largest documents cannot be drawn at all.
• 16- and 32-bit files are shown and saved at 8 bits per channel, because a browser canvas and a standard PNG from it hold 8. 32-bit HDR values are tone-mapped with a simple 2.2 gamma.
• Editing. This is a viewer: it does not change or re-save the PSD.

Useful to know about PSD files

Why other programs show a different picture

Most viewers other than Photoshop (macOS Preview and Quick Look, many converters and image hosts) show only the flattened image stored in the file. If a PSD looks blank or white in them, it was very likely saved without Maximize compatibility, and only software that re-composites the layers can show it.

PSD versus PSB

A PSD is limited to 30,000 pixels on each side and 2 GB. Photoshop's Large Document Format, PSB, raises the limit to 300,000 pixels per side and lifts the 2 GB file-size cap. Both start with the bytes 8BPS; the next two bytes are 1 for PSD and 2 for PSB.

Getting a single layer out

Click the layer, then “Save layer as PNG”. The PNG is cropped to the layer's bounds and keeps its transparency, which is what you usually want for a logo or cut-out. Hidden layers can be saved this way too.