Tracking vs. Kerning: What's the Difference?

Tracking and kerning get used almost interchangeably in casual conversation, but they're doing genuinely different jobs, and mixing them up is a common source of confusion when you're trying to fix spacing that looks off. The short version: kerning is about specific letter pairs, and tracking is about a whole range of text at once.

Kerning: fixing individual pairs

Kerning adjusts the space between one specific pair of letters. Some letter combinations, if spaced with a uniform gap, look like they have too much air between them — a capital "A" next to a capital "V" is the classic example, since the diagonal strokes lean away from each other and leave a visual gap wider than the space next to two straight-sided letters. Kerning pulls that specific pair closer together (or, less often, pushes a pair apart) to even out the visual rhythm.

Most typefaces ship with a kerning table built in — a list of problem pairs and how much to adjust each one — so kerning often happens automatically the moment you type. Manual kerning comes in when you're setting a headline or logotype at large size, where every letter pair is magnified enough that even small spacing irregularities the built-in table didn't anticipate become visible, and a designer adjusts pairs by eye.

Tracking: adjusting a whole range uniformly

Tracking, by contrast, applies one uniform adjustment across an entire selection of text — a word, a line, a whole paragraph. It doesn't care which specific letters are next to each other; it just adds or removes the same amount of space everywhere. You'd use tracking to loosen up a line of small caps so the letters don't feel like they're crowding together, or to tighten a large display headline so its letters don't look like they're floating apart.

Because tracking is uniform, it's the tool for a whole-block decision — "this heading needs to feel more open" or "this line needs to feel tighter" — while kerning is the tool for a local, pair-by-pair correction once the overall tracking is already set the way you want it.

Different units, same underlying idea

Both tracking and kerning are ultimately expressed as a fraction of the em (the font size), but different software displays that fraction differently. CSS's letter-spacing property takes a raw em or pixel value. Page-layout tools like Adobe InDesign and Illustrator historically use thousandths of an em for tracking, so a value of "20" means an extra 0.02em between each character. Some interfaces just show a plain percentage. None of these are actually different concepts — they're the same fraction-of-the-em idea, expressed in different units for historical and interface reasons.

A size-dependent rule of thumb

One widely used guideline is that tracking should move in the opposite direction from font size: the bigger the type, the tighter (more negative) the tracking should be, and the smaller the type, the more positive tracking helps. This is because the same absolute gap between letters looks proportionally larger at bigger sizes — a gap that reads as comfortable at 12 points can look loose and disconnected once the same letters are blown up to 72 points for a poster headline. All-caps settings are a related special case: because capital letters lose the varied silhouette that lowercase ascenders and descenders provide, a touch of extra tracking often helps keep individual words from reading as one dense, undifferentiated block.

Putting the two together

In a typical workflow, you'd set the tracking for a whole heading or paragraph first, getting the overall density right, and then zoom in and kern individual pairs that still look off once the general spacing is settled. Doing it in the other order — kerning pair by pair before you've settled on an overall tracking value — usually means redoing the kerning once the tracking changes, since a kerning adjustment made at one tracking value may no longer be the right amount once the surrounding letters have moved.

Metric kerning vs optical kerning

Most design software offers a choice between two automatic kerning modes, and it's worth knowing what each one is actually doing. Metric kerning reads the kerning pairs the type designer built into the font itself — a hand-tuned table of specific letter combinations and how much to adjust each one, based on the designer's own judgment about how their particular letterforms sit together. Optical kerning ignores that table and instead measures the actual black shapes of each glyph and calculates spacing algorithmically, which can be a useful fallback for a font with a sparse or nonexistent kerning table, but it's working from raw shape, not from the designer's intent, so it occasionally gets a pair wrong that the font's own metric table would have handled correctly. As a default, metric kerning is the safer choice for a well-built font; optical kerning is worth reaching for specifically when you notice gaps a font's built-in table missed, often in unusual letter combinations like numerals next to punctuation.

How far negative tracking can go before it hurts recognition

Tightening tracking is a normal, useful move at display sizes, but it has a practical floor. Push it far enough and letters begin to touch or overlap, which does more than look cramped — overlapping strokes can merge two adjacent letters into a shape the eye misreads as a single, different character, which defeats the entire purpose of setting text in the first place. Readability research broadly agrees that severely reduced letter-spacing measurably slows recognition and increases errors, though exactly how much tightening is "too much" varies by typeface, weight, and the specific letters involved, so it's not a number that transfers cleanly from one design to another. The practical test is simple: after tightening a headline, read it at a glance from a normal viewing distance and check whether any two letters have started to visually fuse. If they have, you've gone further than the design can support, regardless of what value is showing in the tracking field.

More kerning pairs worth knowing by eye

Beyond the classic "AV," a handful of other combinations reliably need a kerning adjustment because of how their strokes meet: capital "T" followed by most lowercase letters (the crossbar overhangs, leaving extra space underneath it), "Wa" and "Yo" (a wide diagonal letter followed by a round one, echoing the same gap problem as "AV"), "Fa" and "Fe" (the F's arm leaves a gap above whatever follows), and "LT" or "AT" in all-capital settings (diagonal or open shapes meeting a straight vertical). None of these are arbitrary; each one comes from the same underlying geometry — two letters whose outer edges don't run parallel leave more visual air between them than two letters with straight, parallel sides, even when the raw horizontal distance between their reference points is identical. Recognising this small set of shapes on sight is most of what "having a good eye for kerning" actually consists of.

Bringing it together in a lettering layout

On a poster or lettering piece, the practical order looks like this: rough in the layout and set a provisional tracking value for each block of type, get the headline-to-body hierarchy feeling right at a glance, and only then zoom in on the headline — the place large type and tight viewing distance make kerning pairs most visible — and nudge individual pairs by eye. Body copy rarely needs manual kerning at all; it's set small enough, and read quickly enough, that a font's built-in metric table is doing all the work you need. Save the fine, letter-by-letter attention for the handful of large-scale words where every pair is magnified enough to matter.

Why the units all express the same fraction differently

It's worth pausing on why the industry ended up with three parallel units for the same idea. CSS's letter-spacing takes a plain length — an em value, or a pixel value the browser converts internally — because CSS generally favours expressing sizes as simple length units. Page-layout software adopted thousandths of an em because tracking adjustments in print production are typically small fractions of a character's width, and a whole-number scale (so "20" instead of "0.02") is easier to type, compare, and record in production notes than a long decimal. A plain percentage is really just the em value multiplied by 100, chosen by interfaces that assume most users think more naturally in percentages than in fractions. None of these is more "correct" mathematically — they're the same underlying value, in em-of-the-font-size terms, formatted for the conventions of the tool presenting it, which is exactly why a tracking converter is useful the moment you move a design between two pieces of software that each picked a different convention.

A note on letter-spacing and word-spacing together

Tracking adjusts the space between letters, but it's easy to forget it also nudges the space between words along with it, since word spaces are themselves affected by whatever tracking value is applied to a run of text. A heavily tracked-out line of small caps can end up with word gaps so wide the individual words start to lose their grouping, reading as a scattered row of letters rather than distinct words. When you're pushing tracking significantly looser — for a wide, airy display treatment, for instance — it's worth checking word spacing specifically, and in some software adjusting it back down slightly on its own, so that the space between words stays clearly larger than the space within a word even after the general tracking has opened everything up.