OpenAnyFile
What is a .aco file?
Photoshop Colour Swatches is a design format developed by Adobe. It is usually created by Adobe Photoshop.
Photoshop's own swatch list; the colours are drawn here.
File details
| Full name | Photoshop Colour Swatches |
|---|---|
| Category | Design files |
| MIME type | application/x-photoshop-aco |
| Signature (magic bytes) | 00 01 or 00 02 |
| Developer | Adobe |
| Opens with | Swatch reader |
| Uploaded? | No — read locally in your browser |
How to open a .aco file
OpenAnyFile routes .aco files to its swatch reader, which shows every colour as a swatch with its value.
- Drop your .aco file on the box above, click it to choose the file, or paste it with Ctrl+V.
- The real format is detected from the file's first bytes — not just its name.
- The file opens in the swatch reader.
- Use fullscreen for a closer look, check its checksums, or download it back unchanged.
What works — and what does not
Works
Viewing and inspecting: every colour as a swatch with its value. Size, type, signature and checksums are always shown.
Does not work
Editing and saving back. OpenAnyFile is a viewer, not an editor — for changes you still need the original app.
Is it safe to open a .aco file online?
Here, yes — because nothing is uploaded. Most "online viewers" send your file to their server. OpenAnyFile reads it with your browser's File API and decodes it on your own device, so there is no copy anywhere else. You can check: open your browser's network tab while opening a file — no upload appears.
Questions about .aco files
Can I open a .aco file without installing software?
Yes. OpenAnyFile opens .aco files in your browser using its swatch reader. You get every colour as a swatch with its value, with nothing installed and no account.
How do I know a file is really a .aco file?
Check its first bytes instead of its name. A genuine ACO file begins with 00 01 or 00 02. OpenAnyFile shows the detected type, so a renamed file is easy to spot.
Is my .aco file uploaded anywhere?
No. The file is read locally by your browser and never sent to a server — it even works offline once the page has loaded.
Does it work on phones?
Yes — on Android and iPhone, in any modern browser. You can also install OpenAnyFile as an app.
Related formats
Other formats from the same family:
Format facts checked and page updated on September 25, 2026.