> ## 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, and again after [Unlink custom domain](/api-reference/unlink-custom-domain) to put it back into service. Linking re-enables any email domain configured on it.

<Note>The response body is `null`. Read the domain back with [Get custom domain](/api-reference/get-custom-domain) to see the result.</Note>

Verification does not finish here. Linking asks the provider to start checking DNS; poll [Get custom domain status](/api-reference/get-custom-domain-status) until `verificationStatus` is `verified`.

<Note>A domain is only serving traffic once it is linked and its `last_status_payload.verificationStatus` is `verified`. Adding a domain and linking it are separate steps, and DNS propagation happens outside Base44, so a linked domain can sit unverified for as long as its nameservers take.</Note>



## 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, and again after [Unlink custom
        domain](/api-reference/unlink-custom-domain) to put it back into
        service. Linking re-enables any email domain configured on it.


        <Note>The response body is `null`. Read the domain back with [Get custom
        domain](/api-reference/get-custom-domain) to see the result.</Note>


        Verification does not finish here. Linking asks the provider to start
        checking DNS; poll [Get custom domain
        status](/api-reference/get-custom-domain-status) until
        `verificationStatus` is `verified`.


        <Note>A domain is only serving traffic once it is linked and its
        `last_status_payload.verificationStatus` is `verified`. Adding a domain
        and linking it are separate steps, and DNS propagation happens outside
        Base44, so a linked domain can sit unverified for as long as its
        nameservers take.</Note>
      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, as returned in `id` by [List custom
              domains](/api-reference/list-custom-domains).
            title: Domain Id
          description: >-
            ID of the custom domain, as returned in `id` by [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.
        '422':
          description: Validation Error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/HTTPValidationError'
        '429':
          description: Base44's hosting provider is rate limiting. Retry later.
components:
  schemas:
    HTTPValidationError:
      properties:
        detail:
          items:
            $ref: '#/components/schemas/ValidationError'
          type: array
          title: Detail
      type: object
      title: HTTPValidationError
    ValidationError:
      properties:
        loc:
          items:
            anyOf:
              - type: string
              - type: integer
          type: array
          title: Location
        msg:
          type: string
          title: Message
        type:
          type: string
          title: Error Type
      type: object
      required:
        - loc
        - msg
        - type
      title: ValidationError
  securitySchemes:
    ApiKeyAuth:
      type: apiKey
      in: header
      name: api_key
      description: Personal API key.

````