What is a UDF Reader?

Maybe someone told you you need a UDF reader, or maybe you just ran across the term somewhere. Either way, this page will give you a quick overview of what a UDF reader is, and point you to where you can get more detailed information.

CDs and Filesystems

For Windows to access files on a floppy disk, a hard disk, a CD-ROM, a DVD, or anything else, the data must be arranged in a particular format that Windows can understand. There are many different schemes for storing data files on different types of media, and these schemes are called filesystems.

The first filesystem widely used by Windows for accessing data on CD-ROMs was really built for audio discs. If you think about it, these are discs that are written to once at the factory, and then never modified again. CDs that you could write to with your own computer were pretty much non-existent when Windows was first written. In fact, although even the relatively ancient Windows 95 could read CD-ROMs (like audio CDs, and read-only mass-manufactured CDs), Windows did not offer a built-in means of writing to recordable CDS until Windows XP, many years later.

UDF Means Universal Disk Format

It would be nice if there was only one filesystem for all CDs. Unfortunately, several not-quite-compatible filesystems are in use. In particular, the filesystem typically used when people want to be able to add files to an already-burned (writing to a recordable CD is often called "burning" it) recordable CD is called UDF, which stands for Universal Disk Format. This ability to add data to a recordable CD that already has some data is also called packet writing.

Here's where things get messy. Third-party software like Roxio and Adaptec offered this kind of packet-writing (UDF) support before Microsoft added much support for UDF to Windows. Thus, you could end up burning recordable CDs that you could read fine on your machine (because the same non-Microsoft software you used to burn the CD would also step in and help Windows read it), but would not read correctly on someone else's machine.

Now let's add to the mix the problem that even though UDF is a "standard" filesystem, different vendors trying to implement UDF would make mistakes or have misunderstandings about niggling little details in the specification of the filesystem. Thus, there are even cases where a CD burned by one version of a third-party software package could not be read correctly by a later version of the very same software.

UDF Readers for Backward Compatibility

Here's where the term UDF reader enters the picture. Someone burned a recordable CD (using UDF) and handed it to you, and you can't read it on your machine, quite possibly because the version of Windows you are using does not understand UDF -- or perhaps not that precise flavor of UDF.

Of course, vendors like Roxio and Adaptec know that offering packet writing ability is not so attractive if the resulting recordable CD can't be read on most Windows machines. So, they offer free UDF readers. These are usually free, downloadable pieces of software that give Windows the ability to read recordable CDs that use a UDF filesystem.

More Information on UDF Readers

Most commonly, people reading about UDF readers are in the situation of trying to get data off a CD that Windows can't access correctly. That's why more detailed information on UDF readers is stored in our data recovery section. Depending on your needs, you might want to jump right to determining if you need a UDF reader. If you're already pretty sure you need a UDF reader, you could jump right to where to download a UDF reader.

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