> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://contentful.com/developers/docs/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://contentful.com/_mcp/server.

> **Info**
>
> **Use the [App Framework](/extensibility/app-framework) for any new projects.** We recommend creating apps instead of UI extensions. [Read the app FAQ to learn why](https://www.contentful.com/help/contentful-app-framework-faq/).

UI Extensions allow you to customize and extend the functionality of the Contentful web app's entry editor. Extensions can be simple user interface controls, such as a dropdown, or more complex micro applications such as our Markdown editor.

To get started with UI extensions please refer to our dedicated [extensibility](/extensibility/app-framework) section.

An extension resource describes to which fields your extension can be applied and where its code can be found. The following is a list of the properties of an extension resource:

| Property   | Required | Type              | Description                                                                                                                           |
| ---------- | -------- | ----------------- | ------------------------------------------------------------------------------------------------------------------------------------- |
| name       | true     | String            | Extension name                                                                                                                        |
| fieldTypes | false    | Array\[Object] \* | Field types where an extension can be used                                                                                            |
| src        | \*\*     | String            | URL where the root HTML document of the extension can be found                                                                        |
| srcdoc     | \*\*     | String            | String representation of the extension (e.g. inline HTML code)                                                                        |
| sidebar    | false    | Boolean           | Controls the location of the extension. If `true` it will be rendered on the sidebar instead of replacing the field's editing control |
| parameters | false    | Object            | Definitions of [configuration parameters](/extensibility/app-framework/app-parameters)                                                |

\* Valid field types are:

* `{type: "Symbol"}`
* `{type: "Text"}`
* `{type: "RichText"}`
* `{type: "Integer"}`
* `{type: "Number"}`
* `{type: "Date"}`
* `{type: "Boolean"}`
* `{type: "Location"}`
* `{type: "Object"}`
* `{type: "Link", linkType: "Asset"}`
* `{type: "Link", linkType: "Entry"}`
* `{type: "Array", items: {type: "Symbol"}}`
* `{type: "Array", items: {type: "Link", linkType: "Entry"}}`
* `{type: "Array", items: {type: "Link", linkType: "Asset"}}`

\*\* One of `src` or `srcdoc` has to be present:

* Use `srcdoc` if you want to host the extension code in Contentful. Note that extensions hosted in Contentful have a size limit of 200KB.
* Use `src` if you host the extension yourself. Note that in this case your extension must be hosted on an HTTPS domain with CORS enabled.

## Extensions collection

[Get all extensions of a space](/references/content-management-api/ui-extensions/get-all-extensions-of-a-space)

[Create an extension](/references/content-management-api/ui-extensions/create-an-extension)

## Extension

Use this endpoint to create a new extension with a specified ID, or to update a specific extension via its ID. When updating an existing extension, you need to specify the last version of the extension you are updating with `X-Contentful-Version`.

[Create or update an extension](/references/content-management-api/ui-extensions/create-or-update-an-extension)

[Get an extension](/references/content-management-api/ui-extensions/get-an-extension)

[Delete an extension](/references/content-management-api/ui-extensions/delete-an-extension)


## API Docs

- UI Extensions [Get all extensions of a space](https://contentful.com/developers/docs/references/content-management-api/ui-extensions/get-all-extensions-of-a-space.md)
- UI Extensions [Create an extension](https://contentful.com/developers/docs/references/content-management-api/ui-extensions/create-an-extension.md)
- UI Extensions [Get an extension](https://contentful.com/developers/docs/references/content-management-api/ui-extensions/get-an-extension.md)
- UI Extensions [Create or update an extension](https://contentful.com/developers/docs/references/content-management-api/ui-extensions/create-or-update-an-extension.md)
- UI Extensions [Delete an extension](https://contentful.com/developers/docs/references/content-management-api/ui-extensions/delete-an-extension.md)

## OpenAPI Specification

The raw OpenAPI 3.1 specification for this API is available at:
- [OpenAPI JSON](https://contentful.com/developers/docs/openapi.json)
- [OpenAPI YAML](https://contentful.com/developers/docs/openapi.yaml)