> ## Documentation Index
> Fetch the complete documentation index at: https://docs.base44.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Link custom domain

> <Info>This API is in beta. Endpoints, fields, and behavior may still change, so avoid depending on it in production.</Info>

Attaches the domain to Base44's hosting and starts DNS verification.

Call this after adding a domain. It's also how you put a domain back into service after [Unlink custom domain](/api-reference/unlink-custom-domain). Linking re-enables any email domain configured on it.

The response body is `null`, so read the domain back with [Get custom domain](/api-reference/get-custom-domain). Verification doesn't finish here. Linking only asks the provider to start checking DNS, so poll [Get custom domain status](/api-reference/get-custom-domain-status) until `verificationStatus` is `verified`.

DNS propagation happens outside Base44, so a linked domain can sit unverified for as long as its nameservers take.



## OpenAPI

````yaml /developers/references/app-management/app-management-openapi.json post /api/apps/{app_id}/custom-domains/{domain_id}/link
openapi: 3.1.0
info:
  title: Base44 App Management API
  version: 1.0.0
servers:
  - url: https://app.base44.com
security:
  - ApiKeyAuth: []
paths:
  /api/apps/{app_id}/custom-domains/{domain_id}/link:
    post:
      summary: Link custom domain
      description: >-
        <Info>This API is in beta. Endpoints, fields, and behavior may still
        change, so avoid depending on it in production.</Info>


        Attaches the domain to Base44's hosting and starts DNS verification.


        Call this after adding a domain. It's also how you put a domain back
        into service after [Unlink custom
        domain](/api-reference/unlink-custom-domain). Linking re-enables any
        email domain configured on it.


        The response body is `null`, so read the domain back with [Get custom
        domain](/api-reference/get-custom-domain). Verification doesn't finish
        here. Linking only asks the provider to start checking DNS, so poll [Get
        custom domain status](/api-reference/get-custom-domain-status) until
        `verificationStatus` is `verified`.


        DNS propagation happens outside Base44, so a linked domain can sit
        unverified for as long as its nameservers take.
      operationId: link_to_render_api_apps__app_id__custom_domains__domain_id__link_post
      parameters:
        - name: app_id
          in: path
          required: true
          schema:
            type: string
            description: ID of the app the domain belongs to.
            title: App Id
          description: ID of the app the domain belongs to.
          example: 6820f3a4e7b91d003c45a1f2
        - name: domain_id
          in: path
          required: true
          schema:
            type: string
            description: >-
              ID of the custom domain. Get this from [List custom
              domains](/api-reference/list-custom-domains).
            title: Domain Id
          description: >-
            ID of the custom domain. Get this from [List custom
            domains](/api-reference/list-custom-domains).
          example: 68b1c0d4e7b91d003c45a1f7
      responses:
        '200':
          description: >-
            The domain is attached and verification has started. The body is
            `null`.
          content:
            application/json:
              schema: {}
        '401':
          description: Missing or invalid credentials.
        '403':
          description: >-
            You don't have access to this app, or you used a workspace API key.
            These endpoints take a personal API key.
        '404':
          description: The app has no custom domain with this ID, or the app doesn't exist.
        '429':
          description: Base44's hosting provider is rate limiting. Retry later.
components:
  securitySchemes:
    ApiKeyAuth:
      type: apiKey
      in: header
      name: api_key
      description: Personal API key.

````