CHM to LRF Converter

Convert CHM to LRF 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 an LRF file?

The LRF (Broad Band eBook) format is a deprecated proprietary eBook format developed by Sony for its PRS-500 and PRS-505 e-reader series. It is a binary format that utilizes a specific XML-based markup internally for layout rendering, supporting hard-coded pagination, vector images, and zlib compression. Unlike reflowable formats, LRF defines static page layouts, which can lead to scaling issues on displays with resolutions differing from the original Sony hardware specifications.

How to open an LRF file

Sony has abandoned LRF in favor of the EPUB standard, meaning modern devices do not support it natively. The most reliable method for opening LRF files on desktop systems is using Calibre or the Summoner application. For viewing on modern e-readers or tablets, conversion to EPUB or PDF via Calibre is the standard technical workflow.

LRF Technical Info

Full Name: Sony Portable Reader Format
Developed By: Sony
Initial Release: 2006
MIME Type: application/x-sony-bbeb

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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 LRF in seconds

Every CHM to LRF 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 LRF via API

Automate CHM to LRF 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-lrf",
    "tasks": {
      "upload-file": {
        "operation": "import/upload"
      },
      "convert": {
        "operation": "convert",
        "input": "upload-file",
        "output_format": "lrf"
      },
      "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.