What ISO Files Are - How to Open and Use Them


Files with the extension ISO are a commonly used file type but I get a lot of inquiries from PC users who do not know what an ISO file is or what to do with one. If you are puzzled by ISO files, here’s what they are all about.

ISO files are simply a way of packaging a lot of files and folders together into a single file with the file extension ISO. They are generally used to create an image of a CD or DVD. Having just one file containing everything is convenient for downloading or for storing on a computer. It is becoming common to distribute programs this way instead of providing physical media. As fewer devices are coming with optical drives, you are likely to encounter ISO files more and more.

A major reason that many average PC users have trouble with ISO files is that Windows XP and Vista do not recognize them natively. If you try to open an ISO file in these older versions of Windows, they do not know what to do with it unless you have installed some third-party software to manage ISO files. However, Windows 7 does have a feature to burn ISO files to a CD or DVD. Windows 8 finally provided a native Windows facility for mounting ISO files.

Burning ISO files to a CD/DVD

One way to make use of ISO files is to burn the file to a physical CD or DVD disc using a process that extracts all the individual folders and files out of the ISO file and places them on the physical media. Windows 7 comes with the built-in Windows Disc Image Burner (not in earlier versions of Windows). Place a blank CD or DVD in your optical drive and double-click the ISO file. Once the disc is burnt, you can use the files and folders the usual way.

Many PCs also come with third-party software for burning discs. If one of these opens when you double-click an ISO file, choose “Burn disc image” or similar command.

There are also free programs for burning CDs or DVDs. Gizmo’s top pick is ImgBurn. Go to Best Free CD-DVD Burning Software for more information.

Mounting an ISO file to emulate a disc

Often it is not necessary to actually burn a physical disc. It is becoming more common to use ISO files directly. Some older programs will only recognize an external disc and if that is the case you can mount the ISO file so that it appears to be on a separate drive. See Best Free CD-DVD Emulation Software.

In Windows 8.x, mounting an ISO file is very easy. Right-click the ISO file and select "Mount" from the context menu.

Reading the contents of an ISO file without unpacking it

Some applications can read an ISO file as if it were a disc. For example, virtual machines can install Windows operating systems straight from the ISO without unpacking it. It is also possible to read contents of an ISO file with the archive program 7-Zip. It’s analogous to reading the contents of a ZIP file. 

Unpacking an ISO file directly to the hard drive or USB drive

It is also possible to use 7-Zip to extract all the files and folders from an ISO file and place them in a folder on the hard drive or on a USB drive. Just use 7-Zip in the same way as with regular archive files. There are also programs like IsoBuster.  

And there you have it – ISO files don't have to be a mystery any longer.

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I have a directory which contains both Windows & Linux, is there a S/W available to create an iso image that works on both Linux & Windows system?
Thank you!

This, in response to patels query below - ISO creation:

Folder2ISO, as mentioned by another commenter. So simple - ditto.

In order to modify an existing ISO you must first extract the all the files to a folder, add or subtract your files as desired, then make a new ISO file.

The simplest, smallest program that I've found that can do all that is ISO Toolkit 5.0 from:

It's only a couple of MB and can even burn the resulting ISO if required.

Are there any useful suggestions for a freeware program that can add files to an existing ISO image? Last time I checked, the only thing I could find was ISO Master, which is presently only available for Linux. (It is, fortunately, included in some versions of Knoppix, so when needed it is at least fairly easy to get running.)

Some programs distributed in ISO format only take up a tiny fraction of a CD or DVD, and it seems wasteful to leave so much empty space.

Use 7-zip to unpack, add files, and use folder2iso to repack. So simple.

The problem is that unpacking an ISO does not necessarily preserve all the content of the ISO, such as the boot sector for "live" CDs. After all, there would otherwise be little reason not to just distribute the ISO as a collection of zipped files, would there?

I do not personally know of one but I suppose you can always unpack an ISO, add the files, and then reform the ISO. Maybe someone else knows of a program.

The title reads: "What ISO Files Are" - but it would be a good addition to the article if you mentioned what "ISO" stands for and why it was invented. Also, what is the difference between using a zip archive to contain the file structure as opposed to the ISO file (aside from the fact that you can mount the ISO).

Another useful article! I think more like these are in order.

I hope this clears more of the mystery surrounding ISOs.
Forgive me if I'm over-repeating information, it's probably a teacher's professional flaw.

CDs needed a format (file system) for storing files, and so a specialized file system was made into an ISO standard: ISO 9660. So basically, ISOs are images (backup archives or exact replicas) of the content on the disc, on which the files are stored in the exact same order (or layout) as on the disc (byte by byte). So just as with ZIP archives, think of them as single files which in fact are a package, they contain the aggregate data of the files on the CD.

Revisions were later added to the ISO 9660 file system standard, such as what is known as the "Joliet extensions" in order to accommodate lengthier file path names in newer operating systems, and other benefits.

A modern file system also meant for use specifically on optical discs is UDF, which was also revised several times and has several advantages over ISO. It is more largely supported on newer operating systems and less on DVD-players, but for the sake of compatibility, either or both of the file systems can be recorded to an optical disc (CD/DVD/Blu-ray) using a burning unit and software.

The term "burner" is generally more often used colloquially than "recorder" and it derives from the fact that the technology involves a laser that operates on the surface of the disc.

As such, an ISO archive, being a backup image (replica into a file) of a disc, could contain both UDF and ISO (+ Joliet optionally) too. That way, if you accessed such a disc from within an older operating system which only supports ISO 9660, some files (with lengthy names) may appear as shorter names for example.

Unfortunately, unlike with other types of archives (such as ZIP), I haven't come across any piece of software that can update/delete specific files within an archive, without recreating the entire archive (edit it in-place). There are however several alternatives to ISOs which have the advantage of compressing the contents (generally resulting in smaller disc images but more processing, just as with ZIP compression), but they are generally proprietary formats. I'm not going to name the software, because they are commercial ones (so not allowed here), but I'm assuming it's safe to mention the file formats as examples: ISO-ZIP (file names with the ISZ extension, probably using similar compression to ZIP) and Direct Access Archive (file names with the DAA extension, using the open-source 7-Zip engine for compressing data). They don't support updating specific files within the archive either though.

Maybe not a well-enough-known feature of optical disc file systems is that they can also be optimized (although not all burning software supports it) to only store duplicate file data once (this applies to both a physical disc and to disc images). Another thing specific to optical discs is that they can contain multiple sessions (most software have an option to leave the disc "open" when burning it, which means to allow adding files later).

This was what I have to add about ISOs and differences between them and common archive formats after having been using them for years, but I'm in no way an authority nor do I have any formal knowledge regarding this subject specifically (that's why I haven't specified numbers when talking about file system limitations).

Tech Tips are intended to be fairly short and not encyclopedic. However, it would be very interesting to have a full article of the type you suggest. We would be very happy to look at it if you would like to submit one. Go to this link http://www.techsupportalert.com/write-for-gizmos.htm and maybe you will become an author of articles for Gizmo's.

The page you need is this: http://www.techsupportalert.com/best-free-cd-dvd-burning-software.htm (burning, not emulating)

Most cd/dvd burning software can create ISOs as well as burn directly to disk. Generally you'll have the option with burning software to burn to disk, or "burn" to hard drive.

Is there any software which can create ISO from the files/folders in the HDD?

BurnAware free has the ability to create ISO image from local files and folders. You have to run the program, and select "Make ISO" feature. You can find BurnAware on this review: http://www.techsupportalert.com/best-free-cd-dvd-burning-software.htm CD Emulators too can be used to create ISO images. Apart from the link which Vic shared, you can also take a look at TotalMounter: http://www.techsupportalert.com/content/totalmounter-free-virtual-cddvd-...

Thanks for the suggestion.

None of the program listed in the suggested link, can CREATE an ISO image FROM the folders/files in the HDD. I understand that these programs can create an image from the existing CD/DVD.

I am looking for a software can allows to pickup files/folders from the HDD and creates an ISO image file, without actually writing into a physical disk.

Thanks in advance.

Quote from the referenced review: "In addition to mounting images to virtual drives, Gizmo Drive allows you to create ISO images from a disk or folder"