# .iso MIME Type: application/x-iso9660-image

> Disk images of an ISO 9660 file system — OS installers and optical disc copies.

- MIME type: `application/x-iso9660-image`
- Extensions: .iso
- Content-Type header: `application/x-iso9660-image`
- Compress in transit: no (already compressed)
- File signature: `43 44 30 30 31` at offset 32769

## Good to know

- Windows and macOS mount ISO files natively. Linux installer ISOs are usually hybrid images you can write straight to a USB stick.
- ISOs are big: make sure the server supports range requests so interrupted downloads can resume.

## Server configuration

### nginx (inside the types block in mime.types)

```
application/x-iso9660-image iso;
```

### Apache (.htaccess or server config)

```
AddType application/x-iso9660-image .iso
```

### Express

```
res.set("Content-Type", "application/x-iso9660-image");
```

### Python

```
import mimetypes

mimetypes.add_type("application/x-iso9660-image", ".iso")
```

### HTML file input

```
<input type="file" accept=".iso,application/x-iso9660-image">
```

## FAQ

### What is the MIME type for .iso files?

`application/x-iso9660-image`.

### What Content-Type header should a .iso file be served with?

`Content-Type: application/x-iso9660-image`. It's already compressed, so servers shouldn't gzip it.

### How can I tell if a file is really a .iso?

Check its bytes rather than the extension: ISO files contain `43 44 30 30 31` (`CD001`) at byte offset 32769. On the command line, `file --mime-type name.iso` does this for you.

## Related types

- [.dmg — application/x-apple-diskimage](https://www.devkult.com/mime/dmg.md)
- [.zip — application/zip](https://www.devkult.com/mime/zip.md)

Open the interactive page: https://www.devkult.com/mime/iso