What is a .ISO file?
Most often, the role of the .ISO file consists in being a disc image, which is one archive containing exact sector-by-sector image of CD, DVD, and other disc-based media. The standard file system in this case will be ISO 9660 defined in specifications of ISO and ECMA as CD-ROM exchange format. Disc images of DVDs and other Blu-rays make use of UDF file system or combination of ISO 9660 and UDF for compatibility purposes.
Examples of use cases for .ISO file include OS installers, system restore, firmware, software distribution, backup of CDs/DVDs and DVD-Video. Operating Systems including Microsoft Windows, macOS, and other desktop systems support mounting of ISO images, providing access to their contents as though they are regular physical disc.
One more case relates to usage of the .iso extension for game console disc images. Files used here have a common extension .iso although sometimes the file system of these archives might be proprietary. For identification one would need header specific to this format, specific size/encryption of the file, and emulation support.
There is also another type of document made by PTC Arbortext IsoDraw for technical illustration. In this case the .ISO is independent from media files. To tell them apart, open them with any media disc image extractor, 7-Zip, file or libmagic command line tools and look for signature CD001 at sector 16.
How to open a .ISO file
Open a .ISO file on Windows
- 1 Go to the folder with your file in File Explorer. Usually, downloaded files end up in Downloads.
- 2 Double-click your .ISO file if you have an app for .iso files on your computer. In case it does not open, move on to step three.
- 3 Right-click your .ISO file -> select .
- 4 Choose Windows File Explorer in the list (Windows 11: choose Always). For Windows 10 -> put a check on "Always use this app to open .iso files" and click OK.
Still not opening? See common problems and fixes, or view it in your browser.
Programs for Windows
- Windows File Explorer free
- 7-Zip open-source
- WinCDEmu open-source
- PowerISO freemium
- UltraISO paid
- ImgBurn free
- VLC media player open-source
- Dolphin Emulator open-source
Open a .ISO file on macOS
- 1 In the Finder app, locate your .ISO file.
- 2 Just double-click your .ISO file in order to automatically launch the program which is connected with it.
- 3 Need another app on your Mac? Control-click the file (or right-click with a mouse). In the pop-up menu select .
- 4 If it isn't in the list, choose and find the application manually.
Still not opening? See common problems and fixes, or view it in your browser.
Programs for macOS
- Disk Utility free
- VLC media player open-source
- Dolphin Emulator open-source
- PCSX2 open-source
- PPSSPP open-source
Open a .ISO file on Linux
- 1 Launch your file manager. Depending on the desktop it may be named Files (GNOME), Dolphin (KDE Plasma), Nemo (Cinnamon) or Thunar (Xfce).
- 2 Double-click the file.
- 3 Or choose another program by right-clicking the file -> .
- 4 Install K3b (if it is not installed on your computer) from the software centre, repository or Flathub.
Still not opening? See common problems and fixes, or view it in your browser.
Programs for Linux
- K3b open-source
- Brasero open-source
- GNOME Disks open-source
- AcetoneISO open-source
- VLC media player open-source
- Dolphin Emulator open-source
- PCSX2 open-source
- PPSSPP open-source
Open a .ISO file on Android
- 1 Launch Files or another file management app.
- 2 In Downloads, find the .ISO file and open it by tapping.
- 3 A list of apps capable of opening the file will be shown. Tap VLC media player and press Always to permanently connect the file type with this app.
- 4 No apps able to open this file? Download VLC media player from the Google Play Store.
Still not opening? See common problems and fixes, or view it in your browser.
Programs for Android
- VLC media player open-source
- Dolphin Emulator open-source
- PPSSPP open-source
Open a .ISO file on iPhone / iPad
- 1 Use the Files app and go to On My iPhone, iCloud Drive or Downloads.
- 2 Tap the .ISO file you want to open.
- 3 If the file can be opened by a built-in iOS app (supported format), it opens automatically.
- 4 Touch and hold the file to get the context menu -> choose -> select VLC media player from the list of apps.
- 5 If there is no such option, download the app first from the App Store and then tap the document again.
Still not opening? See common problems and fixes, or view it in your browser.
Programs for iPhone / iPad
- VLC media player open-source
- PPSSPP open-source
Open a .ISO file online
- 1 Move to the online viewer at the top of this page.
- 2 Drag the file there or select it, and its contents will appear in your browser tab. The file is not uploaded.
Still not opening? See common problems and fixes, or view it in your browser.
More details about opening .ISO files
With Windows from version 8 onwards, the default Image (.iso) file explorer will mount these .iso files right out of the box without any difficulty. First mount the file through clicking the right button on it, choosing Mount from the menu. And then use the opened DVD drive as a normal one and when you want to eject it simply do so by clicking its icon in a similar fashion like you do with the regular DVDs. But using more flexible programs such as WinCDEmu, the same task may be accomplished in an OS which is outdated, and applications like PowerISO, UltraISO, ImgBurn & 7-Zip have capabilities to check or burn the mounted image.
In Mac operating system DiskImageMounter application opens the images and the other related functions may be performed using Mac disk utility. There exists a CLI utility called hdiutil that performs various operations related to ISO. GNOME Disks, K3b, Brasero or archive managements in Linux DE are some typical options in a desktop system where ISO can get easily opened. In Linux command line one can use mounting through loops or opening ISO with CLI tools provided by 7-Zip or libarchive.
There exist many options for an Android smartphone but the best option is based mostly on the type of an .iso file. VLC Media Player in some cases plays a DVD iso file, while PPSSPP supports loading particular PSP images on supported smartphones and PC, and Dolphin emulator loads Wii images. With an iOS system very limited options are found in this regard; VLC player is used to view certain media oriented images and PPSSPP loads images when the system and build both of the app support.
For web uploads usually .isos aren't a good idea as the size and possibly licenses prevent any good uploading. If an .iso cannot get opened through just double-clicking on the file, make sure the file association exists, download checksum and extraction through 7-Zip works fine, while the mentioned one is not in fact a console image or an IsoDraw file.
Technical details
An .ISO file is actually a binary image file and never a text file. Sector size in most CD, DVD, and Blu-ray data structure is usually 2048 bytes, consistent to the standards used by ISO 9660 images and some UDF images. The descriptor of an ISO 9660 image begins at logical sector #16, and the primary idenifier "CD001" begins at byte 32769 from descriptor type character. As mentioned before, a primary way to check if .iso is really and true ISO 9660 format is its signature CD001.
In contrast, a UDF descriptor instead is being used in UDF format instead of simple volume descriptors. Additionally, the compatibility layer often exists in some of DVD images for both UDF and ISO. Console images with .ISO files can be quite distinct due to the existence of any of padding, scrambling, encryption, partitioning, and proprietary file table system. Consequently, usual extractor may reveal little readable content in such case in comparison to the emulator/console programs.
It should be also said that the file-name compatibility will depend upon the filesystems extensions available in the format. Thus, ISO 9660 level #1 permits only 8 characters for a filename along with 3 characters for its extensions. However, the limits are becoming wider in future, and Joliet allows the longer filenames with usage of Unicode. Additional extension, called Rock Ridge, permits POSIX features for the files in disc images.
Also, the file is supposed not to contain separate partition table, but the boot loader and boot files in boot image using the special El Torito specification for bootable PC discs images. The actual ISO file is generally un-compressed but compressed version exists as well. For PSP game files, CSO and CISO formats of compression usually work. The file size of image usually depends on the particular image, being from several Megabytes for rescue disk to the 700 MB for CD disk, 4.7 or 8.5 GB for DVD image. Also the capacity can reach tens of Gigabytes for Blu-rays.
How to convert .ISO files
The best method to obtain files only from ISO is through its extraction into a folder. It can be implemented via 7-zip like: 7z x image.iso -oextracted. The process makes file content accessible but erases ISO features like bootability and boot sectors, sector order, hidden boot catalogs and the metadata about the content stored by the volume.
In case of installers or a Recovery disc loss mentioned properties matters because of the need to be written onto storage and can change boot flags and other properties.
On macOS, there is hdiutil that provides a capability to switch ISO from one format to another, that are: image.iso <-> CDR and DMG. Such commands are the most common ones: hdiutil convert image.iso -format UDRW -o image.dmg and hdiutil convert image.dmg -format UDTO -o image.iso. Yet, DMG to be converted should correspond to certain standard because ISO image for optical disc does not support all DMG features.
ISO images containing DVD video can be changed into .mp4, MKV formats with HandBrake CLI and/or VLC, when the content is unencrypted or legally decrypted first. Menus, chapters with changing angles, navigation in MPEG-2 form will be lost.
Image for a console game should have separate conversion methods. So, Dolphin emulator can create from GameCube, Wii ISOs such formats as RVZ, GCZ, WIA and WBFS, while corresponding PSP tools convert ISO into CSO.
| Convert to | Tool | Command / note |
|---|---|---|
| Extracted folder/files | 7-Zip | 7z x image.iso -oextracted Extracts files from a readable ISO 9660/UDF image; boot sectors and disc layout details are not preserved as normal files. |
| Bootable USB drive | Rufus | Writes operating-system ISOs to USB media on Windows; the USB is overwritten and may not remain a simple file copy of the ISO. |
| DMG | hdiutil | hdiutil convert image.iso -format UDRW -o image.dmg Useful on macOS for writable disk images; bootability may change depending on partition and bootloader contents. |
| CDR/ISO from DMG | hdiutil | hdiutil convert image.dmg -format UDTO -o image.iso Produces a raw optical-style image, often with a .cdr suffix that can be renamed when appropriate. |
| CISO compressed disc image | ciso | ciso 9 image.iso image.cso Common for PSP disc images; compression reduces size but is intended for console-game images rather than general ISO archives. |
| WBFS | Dolphin Emulator | For Wii disc images, Dolphin can convert ISO to WBFS/RVZ; not applicable to normal software or DVD-video ISOs. |
| DVD video file such as MP4 | HandBrakeCLI | HandBrakeCLI -i image.iso -o movie.mp4 --preset "Fast 1080p30" Works for unencrypted DVD-Video images; menus, multiple angles, subtitles, and original MPEG-2 structure may be lost or simplified. |
Common problems and fixes
Windows Explorer may produce "The disc image file is corrupted" error if there is no full download completed, file is not ISO9660/UDF image or contains console structure or some other unsupported one. Check whether file's SHA-256 / MD5 checksum matches one on the website and try it with 7-Zip, WinCDEmu, PowerISO or game-specific emulator if file contains game's dump data.
An error "Couldn't Mount File" in Windows means that it is a sparse file, marked by Mark of The Web or has been blocked, is kept on network volume/drive/mount point, already has been mounted, has been associated with a 3rd-party app. Copy the file to NTFS volume, launch Properties window and click the Unblock button (if exists), restore .iso file association with File Explorer/known mounting software.
For Linux, "wrong fs type, bad option, bad superblock" reported by "mount" usually mean that a file does not meet requirements - is compressed, does not contain required ISO 9660 or UDF structures, is a gaming image with proprietary file system. Use "file," "isoinfo" or "7z l" before you try to mount an iso.
Failure in creation of bootable USB from the image mostly happens due to improper copying of the ISO (as file), selection of the wrong BIOS / UEFI mode, or using image which was not meant to become bootable from USB drives. Consider usage of Rufus/balenaEtcher, "dd", or GNOME Disks.
7-Zip cannot list content but show README only in case of console disc because this disc uses some proprietary file-system structure. Load those files in Dolphin emulator, PCSX2 or PPSSPP.
DVD playback issues may happen for the reason that file is missing VIDEO_TS folder/contents, contains CSS encrypted disc, IFO/BUP is faulty, or does not have support for DVD NAVIGATOR/MPEG-2 codecs. Also large ISO might be failed on FAT32 volume due to limitations of FAT32 file-system 4 GiB limit. ".iso" extension files made by IsoDraw program do not represent disc images (need to be opened using PTC arbortext IsoDraw program).
Security considerations
The .ISO files may have executable code, installer files, auto-run information, bootstrap code, scripts, or any other malicious documents; thus, the .iso file must be viewed as removable storage obtained via the internet. Windows 8 and later disable old AutoRun feature for most removable storage devices, but when you mount such files as an iso, you may use that medium like trusted CD, thus opening the door for malware execution through manual operations by yourself. The bootable .ISO has the capability to format and write information on your hard drive, install your OS, upgrade firmware on devices, and execute the offline tool outside of the running host OS environment; hence, you should be very careful about the sources of bootable ISO and publisher checksums before loading these bootable images in Rufus or a virtual machine environment.
History and versions
The ISO filesystem standard for optical disk drives, ISO 9660, appeared in 1988 as an outcome of development done by DEC, Microsoft, Philips, Sony, et al. In the same way, ECMA-119 or ECMA standard for CD volume and filesystem structure has roots in High-Sierra filesystem from the later period of 1980s. The set of Rock Ridge extension standards (IEEE P1282 standard, SUSP & RRIP) added support for Unix permissions, device files, symlinks, and long filename to ISO 9660 images as well as additional naming functionality. In mid-90s Microsoft introduced long filnames using UCS-2 encoding under the Joliet naming standard for Windows-readable CD-ROMs as common practice. Finally, the El Torito bootable CD-ROM specification specified in 1995 made booting PCs from ISOs normal.
UDF (optical disc standard by the organization Optical storage technology association) has emerged with the arrival of DVD & Blu Ray media & packet writing technologies. UDF 2.60 relates to the application of Blu-Ray media technology. macOS started native mounting of disk images, while Linux started using loop device functionality; finally, Microsoft support for mounting images became widespread from Windows 8 release.
Related formats
Related formats
The .IMG file format denotes an arbitrary file format of a disk image which may refer to a floppy, a hard-disk, a flash, or optical drive. The .IMG file does not imply any specific ISO9660/UDF format content. In turn, the DMG file refers to a proprietary disk image created and used by Apple and featuring various attributes like compression, encryption, check-sums or even multipart images. The DMG file is popular among users of OS X applications yet less portable in creating boot media compared to other solutions. Mixed-mode CDs requires the BIN/CUE pair as being much more reliable compared to an ordinary data ISO. In case of copying the additional structure of optical discs, NRG and MDF/MDS files by Nero and Alcohol 120% correspondingly contain extra information, however, are less recognized compared to .ISO. .VHD and .VHDX target Hyper-V virtual hard disks and full volumes, not read-only optical installs. Windows installer contains WIM or ESD files inside ISO packages.
No comments yet. Be the first to share your experience with this file type.