# fonts.subset

Part of [Fonts](https://kernstra.com/docs/web-sdk/config/fonts) in the Kernstra Web SDK 1.0.0 configuration reference.

- Type: `boolean`
- Default: `false`
- Page: https://kernstra.com/docs/web-sdk/config/fonts/subset

Embed only the glyphs an edit uses. By default an edit embeds the whole font for every face it touches, so a document a customer saves today can be reopened and edited in the same faces any number of times — every glyph is still there. `true` embeds only the glyphs the edit wrote, which keeps exported files small (a few kilobytes per face instead of a few hundred, or several megabytes for CJK) at a price: a later edit of that document that needs a glyph outside the subset falls back to a bundled look-alike, exactly as it does for any subset font other tools produce. Turn it on when file size matters more than round-trip re-editability, for example single-pass workflows or size-capped uploads. Subsetting needs `pdf-subset.bin` to load (see [Engine, binaries and fonts](https://kernstra.com/docs/web-sdk/guides/engine-assets)) and falls back to full fonts, with one console warning, when it does not.

Web page: https://kernstra.com/docs/web-sdk/config/fonts/subset