What are kerning pairs?

Kerning pairs are combinations of two glyphs whose default spacing needs manual adjustment in a font — classics like AV, To, or Ya. Type designers work through a list of such pairs in their font editor and assign each one a kerning value. This tool generates those lists automatically from any character set.

What do the AB, A⇄B, and ABA patterns mean?

AB produces straight two-glyph pairs (AV). A⇄B checks both orders at once: each ABA string such as AVA contains AV and VA, so every unordered pair appears exactly once. ABA wraps every ordered pair in its first glyph (AVA, VAV), which makes spacing easier to judge because the eye compares the gap on both sides of the middle glyph.

How do I use the proof strings in a font editor?

Pick the Glyphs, RoboFont, or FontLab format: pairs are written as /glyphname sequences (production or nice names, with uniXXXX fallbacks) that paste straight into Sample Strings, Space Center, or a FontLab glyph window. For other editors, use a portable newline, spaced, or continuous text format.

Can I preview the pairs in my own font?

Yes. Click “Open working font” or drag an OTF, TTF, WOFF, or WOFF2 file onto the page. The font is read in your browser, every pair’s kern value is measured, and the file is never uploaded. Recent fonts are remembered on this device only, and a demo font is available if you just want to look around.

Which languages and scripts are supported?

There are 46 presets covering Armenian, English, French, German, Spanish, Portuguese, Greek, Hebrew, Arabic, Persian, Russian, Ukrainian, Polish, Czech, Georgian, Hindi, Bengali, Tamil, Thai, Korean, Japanese, Chinese, Vietnamese, Turkish, and more — and you can paste any custom glyph set. Where pair kerning isn’t customary (for example Chinese, Thai, or most Indic scripts), the tool says so instead of scoring it.

What are context control strings like HH and OO?

A standard spacing-proof technique: each pair is set between control glyphs with known sidebearings (straight controls like HH or nn, round controls like OO or oo), so you judge the pair against a stable reference instead of in isolation.

Yes — completely free, no account, no upload. Everything runs in your browser, and your session (characters, settings, flagged pairs) is saved locally between visits.

Release check

Check one font before release: language coverage, critical kerning pairs, vertical metrics, metadata and preflight, with a score and what to fix first. Font files stay in this browser.

Drop a font here

TTF, OTF, WOFF, WOFF2, TTC or OTC. Parsed locally, never uploaded.

or try a demo font:

Audit a source (UFO / .glyphs)

Check critical pairs while you work, before compiling a font. Reads the source’s kerning and groups only; files stay in this browser.

Drop a .ufo folder or a .glyphs file here, or