> 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

Bring your own fonts to personalize your documentation style.

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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