> For the complete documentation index, see [llms.txt](https://gitbook.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gitbook.com/docs/developers/gitbook-api/api-reference/custom-fonts.md).

# Custom fonts

Upload and manage custom fonts for branding or aesthetic purposes. Once added, fonts can be applied to your spaces or sites to achieve a unique look.

## The CustomizationFontDefinition object

```json
{"openapi":"3.1.0","info":{"title":"GitBook API","version":"0.0.1-beta"},"components":{"schemas":{"CustomizationFontDefinition":{"allOf":[{"$ref":"#/components/schemas/CustomizationFontDefinitionInput"},{"type":"object","properties":{"permissions":{"type":"object","description":"The set of permissions for the font definition","properties":{"edit":{"type":"boolean","description":"Can the user edit the font definition"}},"required":["edit"]}},"required":["permissions"]}]},"CustomizationFontDefinitionInput":{"type":"object","description":"Defines a font family along with its various font-face declarations for use in CSS '@font-face' rules.","properties":{"id":{"type":"string","description":"A globally unique identifier for the font definition."},"custom":{"type":"boolean","description":"Whether the font is a custom font. If false, this font is provided by GitBook."},"fontFamily":{"$ref":"#/components/schemas/FontFamily"},"fontFaces":{"type":"array","description":"A list of font-face definitions, specifying variations such as weight and style.","items":{"$ref":"#/components/schemas/FontFace"},"minItems":1}},"required":["id","custom","fontFamily","fontFaces"]},"FontFamily":{"type":"string","description":"The human-readable font-family name used in CSS (e.g., \"Open Sans\", \"Playfair Display\").","minLength":1,"maxLength":50},"FontFace":{"type":"object","description":"A single font-face declaration specifying the weight and source files for a particular variation of the font.","properties":{"weight":{"$ref":"#/components/schemas/FontWeight"},"sources":{"type":"array","description":"Font source files provided in supported formats (e.g., woff2, woff).","items":{"$ref":"#/components/schemas/FontSource"},"minItems":1}},"required":["weight","sources"]},"FontWeight":{"type":"integer","description":"Numeric representation of the font weight (400=regular, 500=medium, 700=bold, 900=black).","minimum":1,"maximum":1000},"FontSource":{"type":"object","description":"A font file referenced within a font-face declaration, specifying the file's location and format.","properties":{"url":{"description":"The absolute or relative URL pointing to the font file.","$ref":"#/components/schemas/URL"},"format":{"type":"string","description":"The format of the font file. Prefer 'woff2' for modern browsers.","enum":["woff2","woff"]}},"required":["url"]},"URL":{"type":"string","format":"uri","maxLength":2048}}}}
```


---

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