Firebase Cloud Messaging API (FCM)

openapi: 3.1.0
info:
  title: Google Firebase Firebase Cloud Messaging API (FCM)
  description: >-
    The Firebase Cloud Messaging HTTP v1 API enables sending notification and
    data messages to client apps on Android, iOS, and the web. It supports
    per-platform message customization, topic messaging, and condition-based
    targeting.
  version: v1
  contact:
    name: Google Firebase Support
    url: https://firebase.google.com/support
  termsOfService: https://firebase.google.com/terms
externalDocs:
  description: FCM HTTP v1 API Reference
  url: https://firebase.google.com/docs/reference/fcm/rest/v1/projects.messages
servers:
  - url: https://fcm.googleapis.com/v1
    description: FCM HTTP v1 API Server
tags:
  - name: Messages
    description: Send messages to devices and topics
security:
  - oauth2: []
paths:
  /projects/{projectId}/messages:send:
    post:
      operationId: sendMessage
      summary: Google Firebase Send a message
      description: >-
        Sends a message to the specified target (device token, topic, or
        condition). Supports notification payloads, data payloads, and
        platform-specific overrides.
      tags:
        - Messages
      parameters:
        - name: projectId
          in: path
          required: true
          description: The Firebase project ID
          schema:
            type: string
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/SendMessageRequest'
      responses:
        '200':
          description: Message sent successfully
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Message'
        '400':
          description: Invalid request
        '401':
          description: Unauthorized
        '403':
          description: Forbidden
        '429':
          description: Too many requests
components:
  securitySchemes:
    oauth2:
      type: oauth2
      flows:
        authorizationCode:
          authorizationUrl: https://accounts.google.com/o/oauth2/auth
          tokenUrl: https://oauth2.googleapis.com/token
          scopes:
            https://www.googleapis.com/auth/firebase.messaging: Send FCM messages
  schemas:
    SendMessageRequest:
      type: object
      required:
        - message
      properties:
        message:
          $ref: '#/components/schemas/Message'
        validate_only:
          type: boolean
          description: Flag for testing without actually sending the message
    Message:
      type: object
      description: A message to send via FCM
      properties:
        name:
          type: string
          description: The identifier of the message (output only)
          readOnly: true
        token:
          type: string
          description: Registration token of the target device
        topic:
          type: string
          description: Topic name to send to
        condition:
          type: string
          description: Condition expression for targeting
        notification:
          $ref: '#/components/schemas/Notification'
        data:
          type: object
          additionalProperties:
            type: string
          description: Arbitrary key-value data payload
        android:
          $ref: '#/components/schemas/AndroidConfig'
        webpush:
          $ref: '#/components/schemas/WebpushConfig'
        apns:
          $ref: '#/components/schemas/ApnsConfig'
    Notification:
      type: object
      properties:
        title:
          type: string
          description: The notification title
        body:
          type: string
          description: The notification body text
        image:
          type: string
          description: URL of an image to display in the notification
    AndroidConfig:
      type: object
      properties:
        priority:
          type: string
          enum: [NORMAL, HIGH]
        ttl:
          type: string
          description: Message time-to-live duration (e.g. 3600s)
        collapse_key:
          type: string
        notification:
          type: object
          properties:
            title:
              type: string
            body:
              type: string
            icon:
              type: string
            color:
              type: string
            click_action:
              type: string
            channel_id:
              type: string
    WebpushConfig:
      type: object
      properties:
        headers:
          type: object
          additionalProperties:
            type: string
        notification:
          type: object
          additionalProperties: true
    ApnsConfig:
      type: object
      properties:
        headers:
          type: object
          additionalProperties:
            type: string
        payload:
          type: object
          additionalProperties: true