The Versioning Machine is a framework and an interface for displaying multiple versions of text encoded according to the Text Encoding Initiative (TEI) Guidelines. VM 4.0 has been updated to be P5 compatable. While the VM provides for features typically found in critical editions, such as annotation and introductory material, it also takes advantage of the opportunities afforded by electronic publication to allow for the comparison diplomatic versions of witnesses, and the ability to easily compare an image of the manuscript with a diplomatic version.

The Versioning Machine is also a tool for textual editors, providing an environment that allows editors to immediately see the consequences of their editorial decisions. The Versioning Machine can be used locally on a Mac or a PC, or it can be mounted on the WWW for public access. The documentation provided with the software not only provides information about the use of the software, but builds upon the Critical Apparatus chapter of the TEI Guidelines to give further guidance to those who wish to use this method of encoding.