ISO (ISO 9660 image) file format

.iso · disk image · introduced 1988 by ISO/IEC

What is a ISO (ISO 9660 image) file?

An ISO file is a sector-by-sector image of an ISO 9660 (or UDF) optical disc. ISOs are the standard way to distribute Linux installers, bootable rescue media, and game discs. Modern Windows can mount an ISO with a double-click and write it to USB with built-in tools.

Most readers reach this page after double-clicking a .iso file and finding their operating system unsure what to do with it. The good news: ISO (ISO 9660 image) is a well-understood format with mature tooling on every major platform. It is supported in one click by mainstream archivers on Windows, macOS, and Linux.

How to extract a ISO (ISO 9660 image) file

Opening a .iso file is straightforward on every modern operating system. The exact steps depend on which platform you are on:

On Windows

Locate the .iso file in File Explorer.
Right-click the file. If you have 7-Zip installed, choose 7-Zip → Extract Here. On Windows 11 the built-in extractor handles ZIP, 7z, RAR and several other formats directly through Extract All…
If prompted, pick a destination folder and click Extract.
The extracted files appear in a folder next to the original archive.

On macOS

Find the .iso file in Finder.
Install The Unarchiver from the Mac App Store, or Keka for both creating and extracting.
Right-click the file → Open With → The Unarchiver (or just double-click after Unarchiver is set as the default).
The extracted folder appears next to the archive.

On Linux

Use your file manager: right-click the archive → Extract Here (file-roller on GNOME, Ark on KDE).

On the command line, run one of:

7z x archive.iso    # works for almost any format

The files appear in the current directory.

How to create a ISO (ISO 9660 image) file

To pack files into a .iso archive, you typically need an archiver that supports writing this format. Not every tool can create every format — for example, only WinRAR can create real RAR files. The sidebar lists the software known to read and write ISO (ISO 9660 image).

On the command line, the canonical create command is:

# Use 7-Zip, PeaZip, or the format's reference tool to create .iso files.

If you regularly create archives at scale, a dedicated archive automation suite can wrap this command in scheduled jobs, integrity checks, and offsite replication.

Strengths

Universal optical-disc standard
Bootable via El Torito
Simple to mount on every OS

Weaknesses and limitations

Legacy 8.3 filenames without Joliet/Rock Ridge extensions
No compression

Typical use cases

Linux installation media
Game and software discs
Bootable rescue USBs

Technical details

ISO (ISO 9660 image) uses the None (filesystem image) algorithm and is identified on disk by the magic byte sequence CD 30 30 31 (offset 0x8001). The standard MIME type is application/x-iso9660-image. The format is an open specification and is free for any use.

Frequently asked questions

Is ISO (ISO 9660 image) safe to open?

Archive files are containers — they are only as safe as what they contain. A .iso from a trusted source is fine; one received from a stranger can hold malicious executables, scripts, or files engineered to exploit bugs in your archiver. Always keep your archiver updated, and never run unknown executables that come out of an archive. A safe workflow is to extract into a sandbox and scan the contents before opening anything.

What is the maximum file size?

Modern implementations support archives in the multi-terabyte range. The practical limit is your filesystem (FAT32 caps at 4 GB; ext4, NTFS, APFS, and exFAT all comfortably handle multi-TB files).

Can I password-protect a ISO (ISO 9660 image)?

Some archivers can wrap ISO (ISO 9660 image) files in an encrypted container, but the format itself does not always include built-in encryption. Check your archiver's documentation.

How does ISO (ISO 9660 image) compare to other formats?

See our format comparison pages such as ZIP vs 7z, ZIP vs RAR, and tar.gz vs tar.xz for side-by-side feature tables.