CHM

CHM files are compressed HTML files, which are basically the format for help files in Windows.

Troubleshoot

Navigation to webpage was canceled

• The .chm file is on a network or remote drive. Try copy it on a local drive and open it from there
• The .chm file was downloaded from the Internet, and blocked by Windows. In Windows Explorer, right click on the file → Properties..., then in the General pane → click on Unblock.

CHM empty (blank)

• Import the following registry file [1] [2]:

REGEDIT4
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp]
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp\1.x\ItssRestrictions]
"MaxAllowedZone"=dword:00000001

Viewing in Linux

(list from [3]):

gnochm

Viewer on Gnome — deprecated

kchmviewer

Viewer for KDE — ugly, no full support of tabs, etc

wine

Use windows help file viewer under wine:

wine hh.exe helpfile.chm

xChm

A .chm file viewer that is independent of the graphical environment

Firefox plugin - CHM Reader or ChmFox

Ok, I admit it, this is the best viewer of all on Linux. Perfect rendering, fast.

It also include a sidebar to navigate through the CHM Contents and Index, and we can navigate back and forth using mouse gestures.

Actually even much better than the default reader, so even on Windows this is a better choice.

Okular

The pdf file viewer under kde, which can also show .chm files — not anymore ! Support has been removed

Otherwise a quick and dirty trick is to unpack the .chm file and to open up the index.html file.