.chm Help Files Open With an Error or are Blank

Updated Aug 4, 2023

Issue Details

  • I have downloaded NI's CHM Help files or CHM's in a ZIP file. When I open the CHM file, all the pages in the help file are empty. I can see all the topics and tree structure, they open up, but the pages are blank.  Is there a local security policy that I am unaware of?
  • Whenever I open a .chm help file, I get a page load error that says
    • Navigation to the webpage was canceled 
    • The address is not valid.


To display the NI help file, try the troubleshooting steps below.
  • Certain versions of Microsoft Windows block .chm help files as a security measure to prevent the spread of malicious code. If you're certain that the .chm help files you're trying to view comes from a trusted source, the following procedure will unblock a particular .chm help file so that the content will display:
  1. Right-click on the help.chm help file in Windows Explorer and select Properties:
  1. At the bottom of the General Properties pane, click Unblock, then click Apply.
  1. Repeat this procedure for all help.chm files you want to open. Again, this is an issue with Microsoft's security settings and is implemented to prevent the spread of malicious code.

Additional Information

  • These issues can also occur when opening the .chm file from a .zip file that has not been unzipped and saved on your computer. If your .chm file is part of a zipped file or folder, unzip it before attempting to open the .chm file.
  • Another reason behind this behavior is if the .chm files are moved from their original location. If this is the case, place them back to their original location. 
    Create a local copy of the .chm file on your C:\ drive if one does not already exist.