How to audit the kerning pair table of any font
- Step 1Drop your font — TTF, OTF, WOFF, or WOFF2. The auditor parses kern + GPOS tables via opentype.js.
- Step 2Set the Top-N limit — Default 50 — covers the most impactful pairs. Increase to 500 for full audit. Smaller numbers are easier to scan visually.
- Step 3Review the JSON — Each pair: left/right glyph indices, kerning value (in font units), and sample characters. Negative values pull glyphs together (AV, To). Positive values are rare.
Frequently asked questions
Why are some pairs zero?+
Pairs with kerning value 0 are filtered out — they don't represent real kerning. The output only shows pairs that actually adjust positioning.
Why does my font show no kerning pairs?+
Modern variable fonts often pack kerning into compact GPOS class lookups instead of explicit pairs. opentype.js can't fully enumerate class-based GPOS — try a different font for comparison, or use desktop fonttools for class-aware extraction.
What's a typical kerning value?+
Most pairs range from -100 to +20 font units (out of 1000–2048 UPM). AV, To, Wa: -50 to -100. Tab, Th: -10 to -30. Positive values: very rare except slab serifs and some monospaced.
Privacy first
Every JAD Font tool runs entirely in your browser using opentype.js and the wawoff2 WASM Brotli encoder. Your fonts never leave your device — verified by zero outbound network requests during processing.