Kerning Lab
Feel the difference between metric and optical spacing by adjusting it yourself, then see exactly which letter pairs need it most. Runs in your browser — no server call, no tracking.
Your Text
Notorious Pairs
These letter combinations create visual gaps or collisions at their default metric spacing — click to load one into the practice field above.
Kerning vs. Tracking vs. Leading
Kerning: adjusting space between one specific letter pair (AV, To, We). Tracking: uniform spacing applied across all characters at once. Leading: vertical space between lines of text, named after the strips of lead type-setters inserted between rows of metal type. Good typography balances all three.
Metric vs. Optical Kerning
Metric kerning uses pre-defined pair values built into the font file — fast, consistent, but generic. Optical kerning calculates spacing live from each glyph's actual shape — slower to compute, but adapts to unusual combinations metric tables miss. At display sizes (headlines, logos), optical often outperforms metric.
Where the Word Comes From
"Kern" originally meant the part of a metal type piece that projected beyond its body block, letting adjacent letters like f and i tuck closer together without physically colliding. Compositors set this by hand for centuries after Johannes Gutenberg's movable type (c. 1450) — kerning was a purely physical, mechanical constraint long before it was a software slider.
From Metal to Software
Digital kern-pair tables arrived with PostScript Type 1 fonts (Adobe, 1984), letting type designers embed hundreds of adjustment pairs directly in a font file. Hermann Zapf — designer of Palatino and Optima — was an early advocate for craftsmanship-level spacing control carrying over from hand-set metal type into digital fonts.