API & OpenType reference

slab.js

slabify(el, { min = 8, max = 1200, lineHeight = 0.88, refine = true, mode = 'auto' });
slabAll(selector = '[data-slab]', opts);   // every matching element

slabify canvas-measures the text, packs words into lines of equal width, sizes each line to fill the measure, gates on document.fonts.ready, reflows under ResizeObserver (width-guarded so it can’t loop), keeps the real text for accessibility, and honors text-transform.

Option	Default	Meaning
`min` / `max`	`8` / `1200`	font-size clamp (px), so one long word can’t blow the layout
`lineHeight`	`0.88`	line-height for the stacked slab lines
`refine`	`true`	binary-search each line against real rendered metrics for sub-pixel-flush edges
`mode`	`'auto'`	`'auto'` prefers the width axis and falls back to font-size; force with `'width'` or `'size'`

micro.js

micro(selector = '[data-micro]', { quotes = true, hang = true });

Pulls a leading quote into the margin so the text edge is optically flush, and curls straight quotes. No-ops where the browser hangs punctuation natively (Safari). Entirely optional.

CSS utility classes

Class	For
`ht`	base layer (kerning, ligatures, optical sizing, balanced headings, measure) on a wrapper
`ht-tnum` / `ht-data`	tabular figures / tabular + slashed zero
`ht-onum` / `ht-lnum`	oldstyle / lining figures
`ht-zero`	slashed zero
`ht-smallcaps`	true small caps
`ht-caps`	ALL-CAPS with case-sensitive forms + tracking
`ht-frac`	diagonal fractions (scope tightly)
`ht-justify`	justified body copy with hyphenation (needs a `lang` attribute)
`ht-dropcap` / `ht-hang`	drop cap / hanging punctuation
`ht-measure` / `ht-display`	readable measure cap / fluid display size

Variable-font axes

Prefer the mapped CSS property over raw font-variation-settings, which sets all axes at once and bypasses the cascade.

Axis	Mapped property
`wght`	`font-weight`
`wdth`	`font-stretch`
`slnt`	`font-style: oblique <deg>`
`ital`	`font-style: italic`
`opsz`	`font-optical-sizing: auto`
`GRAD`	`font-variation-settings: "GRAD" <n>` (weight without reflow)

Browser support (mid-2026)

hypertype.css gates each progressive-enhancement feature behind @supports with a fallback, so the CSS-only subset is safe everywhere.

Feature	Chromium	Safari	Firefox	Posture
`text-wrap: balance`	114+	17.5+	121+	ship unconditionally
`text-wrap: pretty`	117+	17.5+	no	enhancement; FF wraps normally
`text-box-trim`	133+	18.2+	no	gate; fall back to padding
`initial-letter`	110+	yes (`-webkit-`)	no	gate; fall back to float drop cap
`hanging-punctuation`	no	10+	no	Safari-only; `micro.js` covers the rest
`hyphens: auto`	88+	yes	43+	safe with a `lang` attribute
`font-optical-sizing`	79+	14+	62+	production-safe
`font-variant-*`	52+	9.1+	34+	production-safe

The full OpenType tag catalog (high-level vs low-level mapping, stylistic sets, swashes, the must-use-the-raw-tag cases), the slab algorithm, and the borrow-vs-reject notes on existing tools are in docs/REFERENCE.md.