CHM to PDF Converter

Convert CHM to PDF online for free. Fast, secure, and high-quality conversion with no sign-up or software required.

Free to useNo file stored beyond 1 hourEncrypted over TLS 1.2/1.3No watermarks

or drag and drop files here

Maximum file size is 1GB

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How it works

Three steps to your converted file

Everything happens in your browser tab - upload, pick a format, download. The heavy lifting runs on our servers.

Upload your file

Drag and drop, click to browse, or paste a URL. Batches take up to 20 files at once - 230+ input formats across video, audio, image, document, and archive types.

Choose an output format

Pick from over a hundred output formats. Filter by category or search by name - every option is open to everyone, no account needed.

Convert & download

Hit Convert and grab your download link moments later. Originals are erased when the job completes; results are cleared within about an hour.

What is a CHM file?

The CHM (Compiled HTML Help) format is a proprietary binary documentation format developed by Microsoft for software help files. It encapsulates a collection of HTML pages, hyperlinks, and image assets into a single LZX-compressed archive, indexed via a binary table of contents (HHC) and keyword index (HHK). The format relies on the Information Tech Storage (ITS) file system structure, allowing for rapid random access and full-text search capabilities within the Windows Help environment.

How to open a CHM file

Windows operating systems provide native support via the built-in Microsoft HTML Help Executable (hh.exe). On macOS and Linux systems, which lack the proprietary Windows API, third-party viewers are necessary. KchmViewer is a standard solution for Linux/KDE environments, while xCHM provides cross-platform compatibility for macOS and BSD distributions.

CHM Technical Info

Full Name: Microsoft Compiled HTML Help
Developed By: Microsoft
Initial Release: 1997
MIME Type: application/vnd.ms-htmlhelp

What is a PDF file?

The Portable Document Format (PDF) is a comprehensive file format, standardized as ISO 32000, designed to present documents consistently independent of application software, hardware, and operating systems. It encapsulates a complete description of a fixed-layout 2D document, including text, fonts, vector graphics, and raster images, based on the PostScript language. Advanced implementations support interactive form fields, JavaScript scripting, 3D objects (U3D/PRC), and various encryption standards.

How to open a PDF file

PDF viewing is natively supported by all major modern web browsers (Chrome, Edge, Firefox, Safari) and most operating systems via built-in previewers. For advanced manipulation, form filling, or pre-press validation, dedicated software such as Adobe Acrobat DC, Foxit Reader, or open-source tools like Ghostscript and Poppler is required.

PDF Technical Info

Full Name: Portable Document Format
Developed By: Adobe Inc. / ISO
Initial Release: 1993
MIME Type: application/pdf

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Why RunConvert

The fastest way to convert any file

Purpose-built for speed, privacy, and breadth of format support.

Convert CHM to PDF in seconds

Every CHM to PDF conversion runs on our servers, so your device stays fast and the output quality stays intact.

Fast, cloud-powered

No queue, no waiting. Files are processed on high-performance servers and returned in seconds, even for large files.

Secure & private

Encrypted in transit and never shared with anyone. Uploads are erased the moment your job completes, and results shortly after.

Free - no account needed

Convert without creating an account - no credit card, no trial clock. Sign in only if you want history and higher daily limits.

Developer API

Convert CHM to PDF via API

Automate CHM to PDF conversions in three steps: create a job, upload your file, then poll for the result.

# 1. Create job
curl -X POST https://api.runconvert.com/v3/jobs \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "tag": "chm-to-pdf",
    "tasks": {
      "upload-file": {
        "operation": "import/upload"
      },
      "convert": {
        "operation": "convert",
        "input": "upload-file",
        "output_format": "pdf"
      },
      "export-result": {
        "operation": "export/url",
        "input": "convert"
      }
    }
  }'

# 2. Upload your file (use upload_url from the response)
curl -X PUT "$UPLOAD_URL" --upload-file input.chm

# 3. Poll for result
curl https://api.runconvert.com/v3/jobs/$JOB_ID?include=tasks \
  -H "Authorization: Bearer YOUR_API_KEY"

Replace YOUR_API_KEY with your RunConvert API key. Get your free API key at runconvert.com/api.