CHM contains compiled and compressed HTML help files for Windows operating system. Such file can store text, images and hyperlinks. Data in the file strictly follows composition standard, and includes index and search utility. CHM are created using dedicated compiler.

CHM files are viewable using a web browser, however some type of archives can only by opened with dedicated web browser or file editor. CHM files are used for storage of structured data in a single file, for example a software instruction manual.