.iso — Disc Image
Archive application/x-iso9660-image
What a .iso file is
A byte-for-byte image of an optical disc or an installer volume.
How to open it
Windows and macOS mount ISOs natively. To make bootable media, write it with Rufus, balenaEtcher or dd.
Worth knowing
Always verify the published SHA-256 of an OS image before writing it — hash it here.
How to identify a .iso file
A file's extension is only its name — renaming a.png to a.iso changes nothing inside. What software actually reads is the magic number, the first few bytes of the file.
| Signature | 43 44 30 30 31 at offset 32769 |
| MIME type | application/x-iso9660-image |
| Category | Archive |
ASCII "CD001", after the 32 KB system area.
# what is this file really?
file mystery.iso
# look at the first bytes yourself
xxd mystery.iso | head -2
head -c 16 mystery.iso | xxd
# Windows PowerShell
Get-Content mystery.iso -AsByteStream -TotalCount 16 | Format-HexFrequently asked questions
What is a .iso file?
A byte-for-byte image of an optical disc or an installer volume.
How do I open a .iso file?
Windows and macOS mount ISOs natively. To make bootable media, write it with Rufus, balenaEtcher or dd.
Is .iso safe to open?
The archive itself is inert, but its contents may not be. Extracting a .iso from an unknown sender is how a lot of malware arrives — check what is inside before running anything.
Can I change a file's extension to convert it?
No. Renaming changes the label, not the bytes. The one place it appears to work is between formats that genuinely share a container — renaming .docx to .zip works because a DOCX is a ZIP. Everything else needs a real converter.