Inspect a font file
Read a TTF/OTF/WOFF font's name table, glyph list or metrics table: one parse, three views. Nothing is uploaded.
Runs on your device. The file is never uploaded.
Inspect a font file parses a TTF, OTF or WOFF and prints one of three reports. Summary names the family, the outline format, the glyph count, unitsPerEm and whether a GPOS table is there. Glyphs lists every glyph with its code point and advance width; metrics adds italic angle, cap height and weight class. It returns text, never a file.
Questions
What does it tell me about a font?
Three views, chosen with the detail setting. The default, summary, gives the family and subfamily names, whether the outlines are OpenType CFF or TrueType glyf, the glyph count, unitsPerEm, ascender and descender, and whether a kerning GPOS table exists. Set detail to glyphs for a per-glyph list, or to metrics for typographic measurements.
What is in the glyph list?
One line per glyph in font order, with its index, its Unicode code point and the character itself when it has one, or the glyph name when it does not, plus the advance width. It is the quickest way to find out whether a font covers the characters you need before subsetting it.
What does the metrics view show?
unitsPerEm, ascender, descender, italic angle, underline position and thickness, and cap height, x-height and weight class from the OS/2 table. Values a font does not carry are shown as n/a rather than as zero, so you can tell a missing measurement from a real one.
Why does it show the wrong family name, or none?
It should not. Name records can live under any of three platform entries, and this tool checks the Unicode, Windows and Macintosh entries in turn instead of trusting the first one that exists, which is what makes real-world fonts with Windows-only names report correctly. A font with no English name record at all reports no family name.
Which font files can it read?
TTF, OTF and WOFF. Anything else, WOFF2 included, is refused with "not a font opentype.js can read" plus the parser's own reason, and a reminder to check that the file is not truncated and that its extension matches its contents. The result is a text report, not a file.