How to Open CHM Files on PC and Mac: A Comprehensive Guide

CHM, or Compiled HTML Help, is a file format primarily used for documentation and help files, especially within older Windows applications. These files contain a collection of HTML pages, images, and other assets, all compiled into a single, navigable package. While CHM files are native to Windows, accessing them on other operating systems like macOS requires a bit more effort. This comprehensive guide will walk you through various methods to open CHM files on both Windows and macOS, covering both simple built-in options and more advanced alternatives.

Understanding CHM Files

Before diving into how to open CHM files, let’s briefly understand what makes them unique. A CHM file is essentially a compressed archive containing HTML files, images, scripts, and other related content. The format was designed by Microsoft to provide a structured and searchable help system for software applications. These files usually feature a table of contents, an index, and a full-text search function, making navigation and finding relevant information relatively easy.

While CHM was once a dominant format, its usage has declined with the rise of web-based documentation and more modern formats. However, there are still many instances where CHM files are relevant, particularly for legacy applications and software documentation. Understanding how to access these files remains a valuable skill.

Opening CHM Files on Windows

On Windows, opening CHM files is generally straightforward, as the operating system has built-in support for the format. Here are the primary methods:

Method 1: Using the Built-in HTML Help Viewer

Windows comes with a native application called the “HTML Help Viewer” that handles CHM files automatically. This is the simplest method for most users.

Steps:

1. Locate the CHM file: Find the CHM file on your computer. It usually has a .chm file extension.
2. Double-click the file: Simply double-click on the CHM file. Windows should automatically open it using the HTML Help Viewer.
3. Navigate the content: Use the table of contents on the left pane or the index and search functionality to explore the content.

If you encounter any issues, such as the content not displaying correctly or certain security warnings, refer to the troubleshooting section below.

Method 2: Using the Command Prompt (for troubleshooting purposes)

In some cases, especially when dealing with older CHM files, the built-in viewer may have issues with specific security settings. Using the command prompt can sometimes resolve these problems. This method is not ideal for regular access but useful when troubleshooting specific errors.

Steps:

1. Open Command Prompt: Press the Windows key, type cmd, and press Enter to open the Command Prompt.
2. Navigate to the directory: Use the cd command to navigate to the directory containing the CHM file. For example, if your CHM file is located in C:\Users\YourName\Documents, you would type cd C:\Users\YourName\Documents and press Enter.
3. Open the CHM file: Type the full name of the CHM file including extension, e.g., FileName.chm, and press Enter. This should attempt to open the CHM file via the HTML Help Viewer and sometimes bypass security restrictions that could be in place.

Troubleshooting CHM File Display Issues on Windows

Sometimes, even with the default HTML Help Viewer, you might encounter issues with the display of CHM files, such as blank pages or a lack of interactivity. Here are some common fixes:

• Unblock the CHM file: Windows might block CHM files downloaded from the internet due to security concerns. To unblock the file:
  1. Right-click on the CHM file.
  2. Select “Properties.”
  3. In the “General” tab, locate the “Security” section at the bottom.
  4. If there is an “Unblock” button, check the box labeled “Unblock” and click “Apply” and then “OK”.
• Check Internet Explorer settings: Although the CHM viewer is independent, its rendering engine sometimes relies on the settings of Internet Explorer. Resetting Internet Explorer’s settings may fix some display problems:
  1. Press the Windows key, type inetcpl.cpl, and press Enter. This opens Internet Options.
  2. Go to the “Advanced” tab.
  3. Click on “Reset…” to reset IE to its default settings.
  4. Restart your computer for the changes to take effect.
• Use an Alternative Viewer (see the Alternative Viewer section later)
  If all else fails, try to use an alternative viewer as described later in the article.

Opening CHM Files on macOS

Unlike Windows, macOS does not have built-in support for CHM files. Therefore, you need to use third-party software or other workarounds to open them. Here are the most popular options:

Method 1: Using a Dedicated CHM Viewer Application

The most reliable way to view CHM files on macOS is to use a dedicated CHM viewer application. Several such applications are available on the Mac App Store and through various developers’ websites.

iChm

iChm is a popular free and open-source CHM viewer for macOS. It is simple to use and offers a good balance of features.

Steps:

1. Download and Install iChm: Go to the official iChm website or the Mac App Store to download the application. Install it by dragging the application to your Applications folder, or following the installation instructions provided in the dmg if downloaded from the developer website.
2. Open iChm: Launch the iChm application.
3. Open a CHM file: Click “File” -> “Open” or use the shortcut Cmd + O. Navigate to the location of your CHM file and select it.
4. View the content: The CHM file will be loaded in the iChm viewer, and you can navigate through the content using the table of contents and search features.

Chmox

Chmox is another widely used, commercial CHM viewer that offers a clean interface and excellent performance. It is available on the Mac App Store.

Steps:

1. Purchase and Install Chmox: Find Chmox on the Mac App Store, purchase it and follow the installation process.
2. Open Chmox: Launch the Chmox application.
3. Open a CHM file: Click “File” -> “Open…” or use the shortcut Cmd + O. Find your CHM file and open it.
4. View the content: The content will be displayed in the Chmox viewer, allowing you to browse the content as you would using a standard CHM viewer.

Other CHM Viewer Applications: There are several other CHM viewers available on macOS and also available via websites, such as “CHM Reader”. These should perform in a similar fashion. Search the Mac App Store or the internet to find one that best suits your needs.

Method 2: Using a Web Browser with Online CHM Converters

If you do not want to install a dedicated application, you can use online CHM converters to extract the HTML files, allowing you to view them in your browser. This method is less convenient but may work in situations where you only need to access a CHM file occasionally and prefer not to install new software. Note that you should be mindful of uploading sensitive data to online converters.

Steps:

1. Find a reliable online CHM converter: Search online for a “CHM to HTML converter.” Make sure the service you choose looks trustworthy. Examples include OnlineConvert.com or Convertio.co. These websites change from time to time so you may have to search to find a suitable service.
2. Upload the CHM file: Upload your CHM file to the converter website.
3. Convert to HTML: Start the conversion process. The website will extract the HTML content from the CHM file. This will usually be compressed into a zip or similar format.
4. Download the converted files: Download the converted files to your computer.
5. View in Browser: Unzip (extract) the downloaded file. Locate the index.html file or any file that is an html file and open it in your web browser (such as Safari, Chrome, or Firefox). You should be able to view all of the content that is part of the CHM file.

This method is not as elegant as using a dedicated CHM viewer, as the HTML might not be perfectly formatted, and you may lose some interactive elements or navigation features, but it provides quick access to the content without needing to install anything.

Method 3: Using Virtualization or Boot Camp

If you need to use a Windows application that relies on a CHM help file, consider using a virtual machine (such as VirtualBox or VMware Fusion) or using Boot Camp to run Windows on your Mac directly. Once Windows is running, you can use the native HTML Help Viewer as you would on any Windows PC. This method is far more complicated for the simple task of opening a CHM file but may be suitable if you regularly run other Windows applications on your mac.

Alternative Viewer Options for Both Windows and macOS

While the methods mentioned above are the most common for opening CHM files, several alternative viewers may be useful if you encounter problems with default options. These include:

• Calibre: Calibre is primarily an ebook management and conversion tool, but it also supports opening CHM files. It can be downloaded for free on both Windows and macOS. It offers additional options for viewing or conversion.
• 7-Zip: This free open-source archive utility can extract CHM file contents as well as zip/rar etc. This provides an alternate method to extract html and resources to view locally. Download from the 7zip.org website.
• Online CHM Extractors: A wide variety of websites are available to extract CHM files to view the underlying content, be sure to do your research to find a suitable online service.

Security Considerations

While CHM files are generally safe, there are security considerations you should be aware of:

• Avoid CHM files from untrusted sources: CHM files can contain malicious scripts or code. Only open files that come from sources you trust. Be especially careful with files from unknown or untrusted sources as these could potentially be malicious and could harm your computer or steal your personal data.
• Keep your software updated: Ensure that your operating system and antivirus software are up-to-date. Regular updates include security patches which can protect against vulnerabilities in file formats.
• Be mindful of online converters: Be cautious when uploading sensitive CHM files to online converters. Choose converters that have positive reviews and a strong reputation for handling sensitive content.

Conclusion

Opening CHM files on your computer, whether it’s a PC or a Mac, doesn’t have to be a daunting task. On Windows, the built-in HTML Help Viewer usually does the job, but knowing how to troubleshoot problems or use the command line can also help. On macOS, third-party CHM viewers or online converter tools are the way to go. Always be cautious about the source of your CHM files and use security software to protect yourself against malicious content. By following the methods and suggestions provided in this guide, you should be able to access and view the contents of any CHM file with ease. Remember to explore alternative viewers or converters if the standard options do not suit your needs, or if you are experiencing display or security issues. With the correct tools and approach, CHM files will no longer be a problem and can be used as intended – a source of information and knowledge.