What Is a Font Inspector and Subsetter?
This tool parses TrueType and OpenType files locally with opentype.js. It reports naming records, units per em, glyph count, ascender and descender metrics, and mapped Unicode characters. The subset workflow keeps the required .notdef glyph plus every glyph mapped by your text, then writes a downloadable OpenType font.
How to Inspect and Subset a Font
- 1Upload a .ttf or .otf file from your device; parsing happens locally in the browser.
- 2Review the family, subfamily, naming records, metrics, glyph count, and supported-character preview.
- 3Enter the exact letters, numbers, punctuation, and symbols needed by your page or document.
- 4Resolve any unsupported-character warning, build the subset, and download the generated .otf file.
Common Font Inspection and Subsetting Uses
Web font payload experiments
Create a text-specific font for prototypes and compare its size with the original font.
Font coverage checks
Confirm whether a font maps the characters needed for a language, brand name, icon set, or UI.
Typography debugging
Inspect units per em, ascender, descender, names, and glyph counts when diagnosing rendering differences.
Frequently asked questions
Does the subset preserve every OpenType feature?
No. The generated font retains .notdef and the glyph outlines mapped by your text, but advanced shaping tables, variation axes, kerning, hinting, and color-font data may not be preserved by this basic opentype.js rewrite.
Why are some characters reported as unsupported?
The uploaded font does not map those Unicode characters to a glyph. Add a different font or remove the missing characters before generating a subset.
Is my font uploaded to a server?
No. Parsing and font generation happen in your browser, and temporary download object URLs are released when replaced or when you leave the page.