What's a 'UDF' formatted CD? by Leo A. Notenboom UDF format is simply just another way that CDs can be written. What’s a ‘UDF’ formatted CD? ISO 9660 is the standard for CD’s that has been used for many years defining how CD’s are witten. UDF (Universal Disk Format) came along with DVDs and is being used on other media as well. Become a Patron of Ask Leo! and go ad-free! I found this article: Which DVD / CD format: ISO or UDF? that explains in a little more detail. Subscribe to Confident Computing! Tech problem solving & safety tips & a weekly confidence boost in your inbox every week. I'll see you there! Slow Computer? Speed up with my special report: 10 Reasons Your Computer is Slow, now updated for Windows 10. NOW: name your own price! You decide how much to pay -- and yes, that means you can get this report completely free if you so choose. Get your copy now! Related Posts What Are ISO files, and How Do I Open Them? - ISO files are a common disk image distribution format. We'll look at the best ways to open ISO files, as well as a couple of ways to create them. How Do I Install an ISO File that Contains Software? - Some software is distributed as .iso files. I'll look at a couple of ways to install .iso files, or rather, install the software that they contain. How Do I Burn ISO Files? - ISO files are often used to distribute images of CD and DVD data discs. I'll walk through how to burn ISO files to optical media using ImgBurn. Macrium Reflect 2: Creating Rescue Media - The first step after installing any backup software is to create bootable rescue media. I'll show you how to do that with Macrium Reflect.