This is a dedicated tool that converts HTML files into a single CHM file in seconds. It’s known for its "what you see is what you get" interface.
Most Windows versions open CHM files natively. Just double-click the file.
Easy CHM Download: The Complete Guide to Viewing and Managing Help Files
If you just want to open a file you’ve downloaded, you might not even need extra software:
Always run a download through Windows Defender or Malwarebytes.
Are you looking to an existing CHM file to a different format like PDF or Word ?