File extension
.afm
Adobe Font Metrics File Format Specification Version 4.1 (Acrobat)
.afm files are Adobe Font Metrics: plain-text files describing the metrics of a PostScript Type 1 font — character widths, kerning, and bounding boxes — without containing the glyph outlines themselves.
Known meanings
Formats and reference material for .afm
Adobe Font Metrics File Format Specification Version 4.1 (Acrobat)
Adobe Font Metrics File Format Specification Version 4.1 (Acrobat)
Details
Format notes
Adobe Font Metrics (AFM)
AFM is a plain-text format from Adobe that records the metric information of a
PostScript Type 1 font. Crucially, it does not contain the glyph outlines — those
live in the font program itself (a .pfb or .pfa file) — but instead the
measurements a layout program needs to set type: the advance width of each
character, its bounding box, the character-name-to-code mapping, and kerning pairs
that adjust spacing between specific character combinations.
This separation reflects how PostScript fonts were distributed: the printer or
interpreter held the outline program, while applications on the host used the AFM
to compute line breaks, justification, and text positioning without needing the
outlines. Because it is human-readable text organized into clearly labeled
sections (such as StartCharMetrics and StartKernPairs), an AFM is easy to parse
and inspect.
Status And Preservation Notes
AFM is a legacy companion format from the Type 1 era; modern outline formats such as TrueType and OpenType embed their metrics directly, so separate metric files are no longer needed. For preservation of a Type 1 font, the AFM should be kept together with the corresponding outline program and encoding files, since it is only meaningful alongside them.
Security Notes
As simple, well-structured text, AFM poses little parsing risk, but a reader should still handle malformed or truncated metric and kern-pair entries gracefully.
Further Reading
- Adobe Font Metrics File Format Specification:
https://adobe-type-tools.github.io/font-tech-notes/pdfs/5004.AFM_Spec.pdf