.chm files

Common questions

How do I open a .chm file?

On Windows use Microsoft HTML Help viewer (built in); on macOS use xCHM; on Linux use xCHM. Windows' old help-file format — a compressed bundle of web pages with an index.

What is a .chm file?

Compiled HTML Help. CHM packs HTML pages, images and a search index into one file, and was the standard help system for Windows software from 1997 onward. Windows opens it with the built-in viewer, but files downloaded from the internet often show up blank until you right-click, choose Properties and tick "Unblock" — a security measure, since CHM can run scripts.

Can I convert a .chm file?

Yes. It is usually converted to .pdf, .html or .epub, either by exporting from one of the programs listed above or with a format converter.

Related pages

• .pdf — Portable Document Format A fixed-layout document that looks identical everywhere — the format for anythin
• .docx — Word Document (Open XML) The standard Word document since Office 2007 — a zip archive of XML underneath.
• .xlsx — Excel Workbook (Open XML) The standard Excel spreadsheet since 2007, with a million-row limit per sheet.
• .pptx — PowerPoint Presentation (Open XML) The standard PowerPoint deck since 2007.
• .txt — Plain Text File Text with no formatting at all — the format that will still open in fifty years.
• .doc — Word Document (legacy binary) The pre-2007 Word format — still readable, but Microsoft would rather you conver
• .xls — Excel Workbook (legacy binary) The pre-2007 Excel format, limited to 65,536 rows.
• .ppt — PowerPoint Presentation (legacy binary) The pre-2007 PowerPoint format.
• .md — Markdown Document Plain text with a light formatting convention — headings with #, bold with **.
• .rtf — Rich Text Format A formatted document format readable by every word processor since 1987.
• .pages — Apple Pages Document Apple's word processor format — Apple devices and iCloud only.
• .odt — OpenDocument Text The open-standard word processor format, native to LibreOffice.