What is a .cgm file?

This extension has been used by more than one format

7 different formats have claimed .cgm over the years, so two files with the same extension aren't necessarily the same kind of thing.

• Computer Graphics Metafile ASCIIVersion 1 · x-fmt/142
• Computer Graphics Metafile ASCIIVersion 3 · fmt/301
• Computer Graphics Metafile ASCIIVersion 4 · fmt/302
• Computer Graphics Metafile (Binary)Version 1 · fmt/303
• Computer Graphics Metafile (Binary)Version 2 · fmt/304
• Computer Graphics Metafile (Binary)Version 3 · fmt/305
• Computer Graphics Metafile (Binary)Version 4 · fmt/306

How to open a .cgm file

• GIMP (free) and IrfanView open a very wide range of image formats, including obsolete ones.
• XnView MP is the best bet for unusual or legacy image types.
• Your operating system's built-in viewer may work for mainstream formats.

The registry records this extension against Computer Graphics Metafile ASCII, Computer Graphics Metafile ASCII, Computer Graphics Metafile ASCII and others, so software from that family is the most likely match.

How to convert a .cgm file

• Open it in GIMP or XnView and export as .png (lossless) or .jpg (smaller).

MIME type

When a .cgm file travels over the web, servers label it with one of these MIME types:

What's a MIME type?

The technical record

For archivists, developers and the merely curious: these are the PRONOM registry entries for .cgm.

Got another one?