Why does my CHM file show "This program cannot display the webpage" on Windows?

Windows blocks help files downloaded from the internet. Right-click the file, choose Properties and tick Unblock, then open it again - or open it here, where nothing is blocked because no script in it is run.

How do I convert a CHM file to PDF?

Open it here, choose Whole book (or a chapter) beside Print or save as PDF, and pick "Save as PDF" as the printer. Topics come out in contents order, each starting on a new page, with real text that can be searched. For very large references, print one chapter at a time.

Can it open .hlp files?

No. .hlp is WinHelp, the older format from Windows 3.1 to XP, with a completely different structure. This opens .chm files only.

Some pages look plain or a button does nothing. Why?

Help files can run scripts and ActiveX controls, which this page never does, so anything that depended on them - "related topics" buttons, pop-up definitions, expanding sections - is left out. The text, pictures, styles and links all come through.

Is the help file uploaded?

No. It is read in your browser by a copy of the reader served from this site, so nothing about it is sent anywhere.

Stays on your computer How this works

Free CHM file viewer

Open Windows help files (.chm) on any computer - browse the contents, look up the index, search every page, print it or save it as PDF, Markdown or text - in your browser

Drag & drop a .chm help file here, or browse

Compiled HTML Help from any Windows version · works on Mac, Linux and Chromebook · nothing is uploaded

About this CHM viewer

CHM (Compiled HTML Help) is the help format Windows used from 98 to 10: software manuals, SDK and API references, e-books and course notes, all packed into one .chm file. Windows still opens them, but Macs, Linux and Chromebooks have nothing built in, and even on Windows a downloaded .chm often shows blank pages until it is unblocked in its properties.

This page reads the file with chmdec, an open-source CHM reader compiled to run in your browser, and gives you what Windows Help did: the contents tree, the keyword index, and a search through the text of every topic. Topics show with their pictures and styles, and links between them work. Print a topic, a chapter or the whole book, or choose Save as PDF; extract every file inside to a folder; or save the book as Markdown or plain text. Scripts in the help file are never run. It is free to use, with no account and no upload limit, and it runs entirely in your browser: nothing is uploaded, and once you have used it, it keeps working offline.

What you can do

Open .chm help files on Mac, Linux, Chromebook or Windows, with no install and no "unblock" step
Browse the contents tree and follow links between topics, with Back, Previous and Next
Look up the help file's own keyword index
Search the text of every topic
Print a topic, a chapter or the whole book, or save it as a PDF
Extract every file inside, like "hh -decompile", or save the book as Markdown or plain text

How to open a .chm file on a Mac or Chromebook

Drop the .chm file onto the page, or click to choose it.
Pick a topic from the contents, look it up in the index, or search.
Choose Print or save as PDF, Extract all files, Markdown zip or Text to keep a copy.

Questions

Why does my CHM file show "This program cannot display the webpage" on Windows?: Windows blocks help files downloaded from the internet. Right-click the file, choose Properties and tick Unblock, then open it again - or open it here, where nothing is blocked because no script in it is run.
How do I convert a CHM file to PDF?: Open it here, choose Whole book (or a chapter) beside Print or save as PDF, and pick "Save as PDF" as the printer. Topics come out in contents order, each starting on a new page, with real text that can be searched. For very large references, print one chapter at a time.
Can it open .hlp files?: No. .hlp is WinHelp, the older format from Windows 3.1 to XP, with a completely different structure. This opens .chm files only.
Some pages look plain or a button does nothing. Why?: Help files can run scripts and ActiveX controls, which this page never does, so anything that depended on them - "related topics" buttons, pop-up definitions, expanding sections - is left out. The text, pictures, styles and links all come through.
Is the help file uploaded?: No. It is read in your browser by a copy of the reader served from this site, so nothing about it is sent anywhere.

Report a problem or suggest a feature