Convert CHM to HTML — Free Online Converter
Convert Compiled HTML Help (.chm) to HyperText Markup Language (.html) online for free. Fast, secure document conversion with no watermarks or registr...
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How to Convert
Upload your .chm file by dragging it into the upload area or clicking to browse.
Choose your output settings. The default settings work great for most files.
Click Convert and download your .html file when it's ready.
About CHM to HTML Conversion
CHM to HTML conversion extracts the web content from Microsoft Compiled HTML Help files and produces standard HTML that works in any browser on any platform. CHM is essentially a compressed archive of HTML pages with a proprietary wrapper — this conversion removes the wrapper and delivers the underlying web content in its native format.
Our converter decompresses the CHM's LZX-compressed archive, extracts all HTML pages, stylesheets, and images, and assembles them into a clean HTML output. Navigation structure from the CHM's table of contents is preserved as HTML links, making the content browsable without the Windows Help Viewer.
Why Convert CHM to HTML?
CHM files only open reliably in Windows Help Viewer, which is not available on macOS, Linux, iOS, or Android. Extracting to HTML makes the content universally accessible in any web browser on any device. This is the most direct conversion path since CHM is literally compressed HTML.
Web-based documentation systems, wikis, and knowledge bases need HTML content they can import and index. Converting CHM to HTML enables migration from legacy Windows help systems to modern web-based documentation platforms like Confluence, GitBook, ReadTheDocs, or custom wiki systems.
Common Use Cases
- Making Windows help files accessible on macOS, Linux, and mobile platforms via any web browser
- Migrating legacy CHM documentation to web-based knowledge bases and wiki systems
- Extracting HTML content from software SDK help files for hosting on documentation websites
- Creating browsable offline documentation from CHM files without requiring Help Viewer
- Indexing CHM help file content in search engines by converting to standard crawlable HTML
How It Works
CHM uses the ITS (Information Transport Stream) format to package HTML, images, CSS, and metadata with LZX compression. The conversion decompresses the archive, extracts the file tree, resolves internal links between pages, and outputs clean HTML. The CHM's HHC (table of contents) and HHK (keyword index) files are parsed to generate navigation HTML. Image references are updated to point to extracted image files. Our pipeline preserves the original HTML structure as faithfully as possible while removing Windows Help Viewer-specific markup.
Quality & Performance
Since CHM is compressed HTML, the extraction produces essentially the original web content. Text, formatting, images, tables, and hyperlinks are preserved exactly. The main difference is the navigation system — CHM's tree view sidebar is replaced with HTML navigation links. CSS styles from the original CHM are extracted and applied. JavaScript that depends on the Help Viewer's ActiveX controls will not function, but static content converts perfectly.
Device Compatibility
| Device | CHM | HTML |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Partial |
| iPhone/iPad | Partial | Partial |
| Android | Partial | Partial |
| Linux | Partial | Partial |
| Web Browser | No | No |
Tips for Best Results
- 1Host the extracted HTML on any web server for instant cross-platform access to the documentation
- 2Add a responsive CSS framework if the original CHM's HTML uses fixed-width layouts from the early 2000s
- 3Use a static site generator to wrap the extracted HTML in a modern documentation template
- 4Index the HTML content with a search tool like Algolia or Lunr.js to replace the CHM's built-in search
- 5Unblock the CHM file in Windows (Properties → Unblock) before converting to avoid extraction permission errors
CHM to HTML extracts the web content that was always inside the help file, making it universally accessible in any browser. This is the most natural conversion for CHM since the format is literally compressed HTML.