What is a .ai file?
Adobe Illustrator Artwork · Design · Adobe · 1987
AI is Adobe Illustrator's native vector artwork format. Since Illustrator 9 it is actually a specialised PDF, embedding Illustrator's own editable layer and path data inside a file any PDF viewer can also open, which is why an AI preview shows up correctly almost anywhere even though only Illustrator can truly edit it.
What is a .ai file used for?
A modern AI file is a valid PDF with Illustrator-private data appended, so double-clicking one, or opening it in any PDF reader, shows the artwork correctly. Only Illustrator understands the private data that keeps paths, layers and effects fully editable.
Files saved before Illustrator 9 (2001) predate that PDF compatibility and are instead built on plain PostScript, the same lineage as EPS, which is why an old AI file's header starts with '%!PS-Adobe' rather than '%PDF-'.
Because Adobe has never published the format's full internal structure, other vector apps such as Inkscape or Affinity Designer can only partially import an AI file, generally by reading the embedded PDF content and losing Illustrator-specific editability like live effects.
AI supports artboards, layers, gradients, and both vector paths and embedded raster images, the same working-file richness that PSD offers for a Photoshop project.
What opens a .ai file?
The .ai format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list.
Windows
- Illustrator
- Inkscape (partial import)
- Photopea (web)
macOS
- Illustrator
- Preview (view only)
- Affinity Designer (partial import)
Linux
- Inkscape (partial import)
- GIMP (raster import only)
Web
- Photopea
Open a .ai file step by step
- Confirm the file really is a .ai. Drop it into the WhatFileType identifier, which reads its signature in your browser without uploading anything.
- On Windows, open it with Illustrator or Inkscape (partial import).
- On Mac, use Illustrator or Preview (view only).
- On Linux, try Inkscape (partial import) or GIMP (raster import only).
- Still stuck? Convert the .ai to PDF, which opens more widely.
Why can't I open my .ai file?
Almost always because no installed app understands AI. Install one of the apps above, or convert the file to a format your existing software already reads. If double-clicking opens the wrong program instead of nothing at all, the file association is set to the wrong app rather than the file being broken.
The other possibility is that the file is not really a .ai at all. Drop it into the file identifier to check it by its bytes instead of its name. Nothing is uploaded.
How to convert a .ai file
You can convert a .ai file to PDF, SVG, EPS, PNG using a conversion tool or the export menu of an app that opens it.
What is the .ai file signature (magic bytes)?
A .ai file starts with the hex bytes 25 50 44 46 2D, which read as %PDF- in ASCII. Programs identify AI by those bytes, not by the filename, so a renamed file still gives itself away.
These are the documented signatures for AI. For a full breakdown, see the PDF file signature page.
| Hex signature | Offset | ASCII | Note |
|---|---|---|---|
| 25 50 44 46 2D | 0 | %PDF- | '%PDF-' (modern AI, Illustrator 9 and later, is a PDF-compatible file) |
| 25 21 50 53 2D 41 64 6F 62 65 | 0 | %!PS-Adobe | '%!PS-Adobe' (legacy AI, before version 9, is PostScript-based) |
| 25 25 45 4F 46 | end of file | %%EOF | %%EOF closes the file |
AI also ends with a trailer. The bytes 25 25 45 4F 46 appear at the end of the file, so a truncated download is spotted by checking the last bytes as well as the first.
See the full magic-numbers reference for every format.
Frequently asked questions
What is a .ai file?
AI is Adobe Illustrator's native vector artwork format. Since Illustrator 9 it is actually a specialised PDF, embedding Illustrator's own editable layer and path data inside a file any PDF viewer can also open, which is why an AI preview shows up correctly almost anywhere even though only Illustrator can truly edit it.
Can I open an AI file without Illustrator?
Yes, for viewing: since Illustrator 9, an AI file is a valid PDF, so any PDF reader shows the artwork. For real editing, Inkscape, Affinity Designer or the free web app Photopea can import it, though very complex Illustrator-specific effects may not survive.
Why does my AI file open as a PDF?
It essentially is one. Modern Illustrator saves a complete PDF representation alongside its own private editing data in the same file, which is why PDF software can open it, while only Illustrator can access the layers and paths for editing.
Related formats
Sources
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