1 · Add a font
Only subset fonts whose license allows it. Most open-source fonts (SIL OFL, Apache) do. Commercial licenses often require webfont rights.
2 · Characters to keep
For a logo-only font, untick every set above and paste the text here.
Advanced options
Narrow a range to cut file size. Set both ends to the same value for a static font.
3 · Your subset
Loading the font engine…Why subset a web font?
A full font file carries every character its designer drew: Latin, Greek, Cyrillic, Vietnamese, symbols and alternates. An English site might use 200 of 1,500 glyphs, yet every unused glyph is downloaded before your text renders in the right face.
Subsetting removes the glyphs you don’t need, and WOFF2 compresses what remains with Brotli. Together they routinely cut a font by 70–90%, which shortens the flash of fallback text and improves Largest Contentful Paint.
What unicode-range does
The unicode-range descriptor tells the browser which characters a font file covers, and the browser downloads the file only when the page uses one of them. That lets you split a family into a small Latin file most visitors get and an extended file that loads only when needed. Google Fonts works this way.
Preload the file that matters
Browsers discover fonts late, after the CSS loads and text is laid out. A <link rel="preload"> for your main font starts the download immediately. Preload only the one or two files used above the fold, and keep the crossorigin attribute even on your own domain, or the font is fetched twice.
Questions
Is my font uploaded?
No. The subsetter runs HarfBuzz, the text engine used by Chrome, Android and Google Fonts, compiled to WebAssembly inside this page. Your font never leaves your device.
Why are some characters marked red in the preview?
They appear in your preview text but aren’t in the subset, so the browser draws them with a fallback font. Tick the matching set, or add them to “Also keep these characters”.
Will kerning and ligatures still work?
Yes, with the standard features setting. HarfBuzz also keeps any extra glyphs those features need, such as the “fi” ligature.