supports viewing CHM files. Sumatra is free, open-source and supports many other formats, like PDF, ePub, MOBI, XPS, DjVu, CBR, CBZ.
is a cross-platform, open-source CHM viewer. It works on Windows, Mac and Linux.
is a cross-platform, open-source eBook reader that can also read CHM files.
CHM Reader extension for FireFox
is not a stand-alone application but an extension to FireFox which allows reading CHM files directly in that browser.
is a commercial, multi-tab CHM reader and editor.
Details of CHM format
CHM stands for Compiled HTML
and is a format introduced by Microsoft to be used by Windows application to provide documentation.
CHM document is a collection of HTML pages, compressed and packed as a single file. Files are compressed with lzx algorithm
. CHM document also contains additional files like pre-build search index, table of contents structure etc. For the most complete description of the CHM format, you can read Unofficial HTML Help Specification