What happened to multisession ISO?

Before windows incorporated burning into itself, I use to use 3rd party software to burn multisession ISOs (not UDF, which was always hit and miss). Most of the time, multisession worked, even between computers. In the cases where it didn't, I attributed it to incompatibility between all sorts of things that I can't recall now.

I spent two evenings (and much more in the more distant past) reading up on the current Windows capability of burning discs. In recent times, web info indicates that Mastered format is ISO, while Live is UDF. I will be using discs to migrate info between Windows 7 machines, so I suspect (and hope) that there will be no compatibility issues. Though I don't know for sure until I try it. Perhaps the hardware itself can give rise to incompatibilities. In fact, I have no issue with using Mastered, since I burn discs so infrequently that I can afford to waste disc space in order to maximize compatibility.

However, there is a confusion that I'm hoping to get clarification on if only in order to know what's going on. From what I've read, closing sessions applies to Live format and not Mastered. I find this odd, since I was able to work with multisession ISOs before Windows XP without resorting to UDF. Is this just because Microsoft decided not to support multisession ISOs?

P.S. I am working only with data files, not audio/video media.


Excellent Member
Microsoft Community Contributor
I am certainly not an expert on this, but .iso files are images you burn to a DVD. Those are made by some other utility then you can burn them to DVD by selecting "Burn Image" from the burn options. These are normally used for installers and bootable media.

When you talk about Multisession, that was were you burned more than one session on a DVD. I believe those are the ones that need to be closed before being read by another system.

Windows 7 will store files and allow you to burn them later. But when you insert a blank DVD/CD, you should be given some options. The Data format will probably be the one you want. If you have Autoplay (Control Panel) turned on, you may see a dialog that asks how you want to use the disk, like a USB Flash Drive, or With a CD/DVD player.

Right clicking the DVD Burner in Computer will give you some options.

Sorry, I should have clarified that I do not create .iso files first. I rely on the burning app to do whatever it needs to do in burning ISO 9660. I don't use UDF (or "live" format).

Someone explained to me in another forum that ISO 9660 was hacked to support multisession. My impression is that this is no longer required because since UDF has become much more mature, and I shouldn't expect the compatibility problems of the past. I suspect that part of the reason for the improvement in compatibility is that most machines are Windows XP/7 these days.

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