---
name: Optical kerning
slug: optical-kerning
category: typography
status: published
created: 2026-08-21T00:00:00.000Z
modified: 2026-08-21T00:00:00.000Z
definition: Letting software space letter pairs by looking at their shapes,
  instead of using the pair values the type designer built into the font.
aliases:
  - name: optical spacing
    source: adobe
tags:
  - design-tools
  - fonts
relations:
  contrastWith:
    - kerning
    - tracking
  variantOf: []
  partOf: []
  seeAlso: []
implementations: []
sources:
  - title: Metrics vs. optical spacing (Practical Typography)
    url: https://practicaltypography.com/metrics-vs-optical-spacing.html
demo: inline
exhibit: false
useWhen: a font's own spacing is unreliable at display size
---

Every letter pair gets its space from somewhere. Usually it comes from the font: the
type designer walks the pairs that need help, an open A beside an open V, a T over a
round o, and writes a correction for each into a kern table the shaping engine applies
whenever those two letters meet. Optical kerning throws that table away and computes the
space instead, by looking at the two outlines and measuring the white trapped between
them, then closing or opening the pair until every gap along a line holds roughly the
same amount of white. Adobe's applications offer it as a setting beside the font's own
values, which is where most designers meet the word.

The distinction to hold is with [kerning](/kerning) itself. Kerning is the adjustment:
the space added or removed between one particular pair, whoever decided it and however
it was decided. Optical kerning is one method of deciding it, from the shapes rather
than from the table, so it is a kind of kerning and not an alternative to it. Neither is
[tracking](/tracking), which opens or closes every gap in a run by the same amount and
knows nothing about which two letters it is standing between.

It earns its keep where the table is thin or absent. A face rushed to release, a free
webfont, or a subset that shipped without its `kern` table will leave a display line
visibly lumpy, and computing the space from the shapes is better than trusting values
that were never written. It also handles pairs no table could cover: a [glyph](/glyph)
pulled from a fallback face has no pair value with the letter beside it, because the two
were never in the same font. The cost is symmetrical. Run it over a face whose designer
spaced it carefully and it overrides months of judgement with an average, flattening the
deliberate looseness after a capital or the tight fit of a designed ligature pair. The
rule of thumb is to reach for it at display sizes, on faces you do not trust, and to
leave a good text face alone.

On the web the choice does not exist. The `font-kerning` property only switches the
font's own table on and off, and no browser computes spacing from outlines, so web
typography is metric kerning or none at all. The specimen on this page shows all three
states anyway: the unkerned pair and the metric one are what the browser really does,
while the optical values were computed ahead of time by rasterizing the two letters,
measuring the white between them, and solving for the offset that matches a reference
pair. That is why the three bars land level only in the optical setting, which is the
whole claim the method makes.