In typography, kerning is the process of adjusting the spacing between characters in a proportional font, usually to achieve a visually pleasing result. Kerning adjusts the space between individual letter forms, while tracking (letter-spacing) adjusts spacing uniformly over a range of characters. In a well-kerned font, the two-dimensional blank spaces between each pair of characters all have a visually similar area.
The related term kern denotes a part of a type letter that overhangs the edge of the type block.
The human perception of kerning can vary with the intraword and interword spacing during reading. A visually pleasing result, even with no "kerning control", can be achieved with some control of the space between letters.
For instance, on webpages with CSS1, a standard dating back to 1996, the letter-spacing property (illustrated) offers some control for lost or enhanced "kerning perception"—kerning can be simulated with non-uniform spacing between letters. The standard CSS3 (scheduled for 2014) includes the font-kerning property, which allows complete control of kerning.
For rather more technical reasons, some have proposed to replace (at least some) OpenType-style GPOS kerning with spacer glyphs using OpenType's Glyph Substitution Table (GSUB).
