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

# Send an event

> Send events to trigger workflows.

<Note>Provide either an `email` or `userId` value or both to identify the contact. If both are provided, the system will look for a contact with either a matching `email` or `userId` value. If a contact is found for one of the values (e.g. `email`), the other value (e.g. `userId`) will be updated. If a contact is not found, a new contact will be created using both `email` and `userId` values.</Note>


## OpenAPI

````yaml /openapi.json post /v1/events/send
openapi: 3.1.0
info:
  title: Loops OpenAPI Spec
  description: This is the OpenAPI Spec for the [Loops API](https://loops.so/docs/api).
  version: 1.21.0
servers:
  - url: https://app.loops.so/api
security: []
tags:
  - name: API key
  - name: Audience segments
    description: View audience segments
  - name: Campaigns
    description: Create and manage email campaigns
  - name: Campaign groups
    description: Organize campaigns into groups
  - name: Components
    description: View email components
  - name: Configuration
    description: View configuration settings
  - name: Contacts
    description: Manage contacts in your audience
  - name: Contact properties
    description: Manage contact properties
  - name: Email messages
    description: Manage email message content for campaigns
  - name: Events
    description: Trigger workflows with events
  - name: Event patterns
    description: View workflow event patterns
  - name: Mailing lists
    description: View mailing lists
  - name: Themes
    description: View email themes
  - name: Transactional emails
    description: Create, manage, and send transactional emails
  - name: Transactional groups
    description: Organize transactional emails into groups
  - name: Uploads
    description: Upload image assets
  - name: Workflows
    description: View and mutate workflow graphs
  - name: Workflow nodes
    description: View and mutate workflow nodes
paths:
  /v1/events/send:
    post:
      tags:
        - Events
      summary: Send an event
      description: Send events to trigger workflows.
      parameters:
        - in: header
          name: Idempotency-Key
          description: >-
            Include a unique ID for this request (maximum 100 characters) to
            avoid duplicate emails.


            The value should be a string of up to 100 characters and should be
            unique for each request. We recommend using V4 UUIDs or some other
            method with enough guaranteed entropy to avoid collisions during a
            24 hour window.


            This endpoint will return a `409 Conflict` response if the
            idempotency key has been used in the previous 24 hours.
          schema:
            type: string
            maxLength: 100
      requestBody:
        description: >-
          Provide either `email` or `userId` to identify the contact ([read
          more](https://loops.so/docs/api-reference/send-event#body)).<br>Event
          properties will be available in emails sent by this event. Values of
          properties can be of type `string`, `number`, `boolean` or `date`
          ([see allowed date
          formats](https://loops.so/docs/events/properties#important-information-about-event-properties)).<br>Make
          sure to create the properties in Loops before using them in API
          calls.<br>You can add contact properties as keys in this request (of
          type `string`, `number`, `boolean` or `date` ([see available date
          formats](https://loops.so/docs/contacts/properties#dates))).
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/EventRequest'
        required: true
      responses:
        '200':
          description: Successful send.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/EventSuccessResponse'
        '400':
          description: Bad request (e.g. `eventName` is missing).
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/EventFailureResponse'
        '405':
          description: Wrong HTTP request method.
        '409':
          description: Idempotency key has been used.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/IdempotencyKeyFailureResponse'
      security:
        - apiKey: []
components:
  schemas:
    EventRequest:
      type: object
      required:
        - eventName
      anyOf:
        - required:
            - email
        - required:
            - userId
      properties:
        email:
          type: string
          description: >-
            The contact's email address. **Required if `userId` is not
            provided.**
        userId:
          type: string
          description: >-
            The contact's unique user ID. **Required if `email` is not
            provided.**
        eventName:
          type: string
          description: The name of the event.
        eventProperties:
          type: object
          description: >-
            An object containing event property data for the event, available in
            emails sent by the event.
          examples:
            - planName: Pro
              importDate: '2021-01-01'
        mailingLists:
          $ref: '#/components/schemas/MailingListSubscriptions'
      additionalProperties:
        oneOf:
          - type: string
          - type: number
          - type: boolean
    EventSuccessResponse:
      type: object
      properties:
        success:
          type: boolean
          examples:
            - true
      required:
        - success
    EventFailureResponse:
      type: object
      properties:
        success:
          type: boolean
          examples:
            - false
        message:
          type: string
      required:
        - success
        - message
    IdempotencyKeyFailureResponse:
      type: object
      properties:
        success:
          type: boolean
          examples:
            - false
        message:
          type: string
      required:
        - success
        - message
    MailingListSubscriptions:
      type: object
      description: >-
        Manage mailing list subscriptions.


        Include key-value pairs of mailing list IDs and a `boolean` denoting if
        the contact should be added (`true`) or removed (`false`) from the list.
      examples:
        - cm06f5v0e45nf0ml5754o9cix: true
          cm16k73gq014h0mmj5b6jdi9r: false
  securitySchemes:
    apiKey:
      type: http
      scheme: bearer

````

## Related topics

- [Events API examples](/docs/api-reference/examples/events.md)
- [Integrately](/docs/integrations/integrately.md)
- [Bubble integration](/docs/integrations/bubble.md)
- [Segment](/docs/integrations/segment.md)
- [Zapier integration](/docs/integrations/zapier.md)