What Is a CHW File?

This is a 'help index file' that stores multiple CHM files

What to Know

  • A CHW file is a Compiled HTML Help index file.
  • Open one with FAR HTML.
  • Use a browser like Firefox to view CHM files.

This article explains what CHW files are, how they're related to CHM files, and how you can open one on your computer.

What Is a CHW File?

A file with the CHW file extension is a Compiled HTML Help index file. It's created when multiple CHM files are merged together.

CHM files are help documents used by some programs to store questions and answers about how a program works or what the different options mean. They're saved in the HTML format, so they can include text, hyperlinks, and images, and are generally viewable in any web browser.

These files, then, are used to keep a table of contents of the information in the different CHM files as well as references to the locations of the CHM files.

Normally, CHW files aren't compressed, so they're typically rather large, but some programs do support compressing them to a much smaller file size.

CHW files that open with FAR

How to Open an CHW File

If you're authoring Windows help files, FAR HTML will open CHW files for editing. This is done through the Authoring > Help File Explorer menu. This program can also compress the CHW down to a smaller file size.

If you just have a CHM file and need to open it to read the help documents, you should be able to use a web browser like Firefox or Safari. If that doesn't work, other programs that work include WinCHM, ChmDecompiler, and Help Explorer Viewer.

If you happen to have a CHW file that isn't a Compiled HTML Help index file, which is possible, then it's unlikely that any of the programs mentioned here can open it. The best thing to do in that situation is to open it as a text file using Notepad++.

You can sometimes pull key text out of the file that can help you determine what type of file it is (audio, document, image, etc.) or even what program was used to create it, which can help you research how to open that specific CHW file.

If you find that an application on your PC does try to open the file, but it's the wrong application, or you'd rather have another installed program open it, see our How to Change File Associations in Windows guide for making that change in Windows.

How to Convert a CHW File

If a CHW file can be converted to another format, it's probably possible with the FAR HTML program mentioned above, but we don't know of any sort of dedicated file conversion tool that can do it. You might normally use a document converter to convert file types like CHW, but this format isn't really the same as other document formats like PDF, DOCX, etc.

If you're wanting to convert a CHM file instead, like to PDF, EPUB, TXT, or other text formats, use Zamzar. Just upload it to that website and then choose which format you want to convert it to.

A similar website, Online-Convert.com, should convert CHM to HTML.

Still Can't Open It?

One reason your file won't open could be that you're misreading the file extension. Some files use a suffix that closely resembles ".CHW" even though the formats have nothing in common.

For example, you might be mixing it up with CHA or CHN, neither of which work in the same way as these help files. Some other examples include CHX and CHD files, which are AutoCAD Standards Check and MAME Hard Disk Image files, respectively.

The same concept applies to CHM files. You might really be using a CHML file that belongs to the Chameleon Encrypted Database file format used by Krasbit software.

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