A font inspector parses the SFNT table directory of a TrueType or OpenType font file, listing its tables and decoding the metadata they hold — family and style names, glyph count, units per em and embedding permissions.
What is the TrueType / OpenType Inspector?
TrueType and OpenType share the SFNT container: a header, a table directory, then the tables themselves, each identified by a four-character tag. The essential ones are head (global metrics and units per em), name (all the human-readable strings), cmap (the character-to-glyph mapping), glyf or CFF (the outlines themselves, the difference between TrueType and PostScript-flavoured OpenType), and OS/2, which carries the fsType embedding permission bits.
Those two facts — what the cmap covers and what fsType permits — answer the questions that actually come up. A missing glyph is a cmap coverage problem, not a rendering bug. And fsType tells you whether a font may legally be embedded in a PDF or served on the web, which is a licensing question with real consequences.
Advanced typography lives in GSUB and GPOS: ligatures, kerning, alternates, contextual substitutions. Their presence tells you whether a font supports the features a design depends on.
How to use the TrueType / OpenType Inspector
- Load the .ttf, .otf or .woff file — it is parsed locally.
- Review the table list and the decoded name records.
- Check the cmap coverage and the fsType embedding permission bits.
When to use it
- Working out why a specific character renders as a fallback box.
- Checking whether a font's licence permits web or PDF embedding.
- Confirming a font has the OpenType features a design requires.
TrueType / OpenType Inspector at a glance
| Container | SFNT — table directory of 4-character tags |
| Outlines | glyf (TrueType quadratic) or CFF (PostScript cubic) |
| Coverage | cmap table maps characters to glyphs |
| Licensing | OS/2 fsType bits set embedding permissions |
Frequently asked questions
What is the difference between TTF and OTF?
The outline format. TrueType uses quadratic curves in a glyf table; OpenType may use either that or PostScript cubic curves in a CFF table. Both live in the same SFNT container, and OpenType adds GSUB/GPOS typography tables.
What does fsType mean?
A field in the OS/2 table encoding the foundry's embedding permissions — installable, editable, print-and-preview only, or restricted. It is a licensing signal that PDF generators and browsers are expected to honour.
Why is a character showing as a box?
The font's cmap has no glyph for that code point, so the renderer substitutes a fallback. Inspecting the cmap coverage confirms it immediately.
Last reviewed · found a mistake? contact@decoder.tools · view as markdown