Common Questions

OpenType features are instructions embedded in a font file that tell the layout engine to substitute or reposition specific glyphs. Activating them swaps in ligatures, switches to small capitals, adjusts figure spacing, or applies stylistic alternates, all within the same file.

In Adobe apps, use the Character panel or the OpenType panel. In CSS, use font-feature-settings: "ss01" 1, "onum" 1, or the higher-level font-variant-* properties. In Figma, select a text layer, open the typography options, and click the Details tab. Figma exposes fewer features than Adobe apps. Support varies widely across applications.

A ligature (liga, dlig) merges two or more glyphs into a single form, the classic example being fi. A stylistic alternate (salt, ss01–ss20) replaces one glyph with a different design, usually without changing its relationship to adjacent characters.

Support is the application's responsibility, not the font's. A font may ship with fifty features; an app must explicitly query and apply them. Word processors typically activate only liga and kern by default. Purpose-built design tools expose more, though rarely everything the font contains.

Yes. Use font-feature-settings: "ss01" 1 in CSS, or the more readable font-variant-* equivalents where they exist. All modern browsers support both syntaxes. Self-hosting the font is recommended. Some CDNs strip features from their distribution builds.

A variable font encodes a continuous range of design variations (weight, width, optical size) as numeric axes rather than separate files. Variable axes and OpenType features are independent systems; both can live in the same .woff2 file. A font can have variable axes with no features, many features with no axes, or both.

Kerning adjusts the spacing between specific glyph pairs (AV, To, Ty) where a uniform advance width produces optically incorrect results. The kern feature is on by default in most design tools. In CSS, enable it with font-kerning: normal or font-feature-settings: 'kern' 1.

A catalogue of typefaces, designers, foundries, and projects, documented through their OpenType features. Each entry covers which features a typeface includes and how those features appear in real design work.

opentype.systems is a project by SEMIREGULAR STUDIO, curated by Dascălu Florin.

The type tester loads a typeface in your browser and lets you toggle OpenType features on and off, adjust variable axes, and edit the sample text live. You can also upload your own font file. Nothing is sent to a server; all processing happens locally in the browser.

The site is set in Recursive by ArrowType, Work Sans by Wei Huang, and Cormorant by Christian Thalmann. All three are open source and available on Google Fonts.

Please send your suggestions to ot.systems@semiregularstudio.com.

Editorial content (descriptions and analysis) belongs to opentype.systems. Sharing and quoting from it is fine; just include a link back to the source. Images belong to their creators. Feel free to contact them directly.