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POST
/
v1
/
events
/
send
Send event
curl --request POST \
  --url https://app.loops.so/api/v1/events/send \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "email": "<string>",
  "userId": "<string>",
  "eventName": "<string>",
  "eventProperties": {},
  "mailingLists": {}
}
'
{
  "success": true
}

​
Request

​
Body

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.
​
email
string
The contact’s email address.
Required if userId is not provided.
​
userId
string
The contact’s unique user ID. This must already have been added to your contact in Loops.
Required if email is not provided.
​
eventName
string
required
The name of the event.
​
eventProperties
object
An object containing event property data for the event. Values can be of type string, number, boolean or date. Read more
​
mailingLists
object
Manage the contact’s 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. Read more
{
  "mailingLists": {
    "cm06f5v0e45nf0ml5754o9cix": true,
    "cm16k73gq014h0mmj5b6jdi9r": false
  }
}

​
Contact properties

You can also include default and custom contact properties in your request body, which will update the contact in Loops. These should be added as top-level attributes in the request. Contact properties can be of type string, number, boolean or date (see allowed date formats). 
{
  "email": "hello@gmail.com",
  "eventName": "signup",
  "firstName": "Bob", /* Contact property */
  "plan": "pro" /* Custom contact property */
}
There are a few reserved names that you cannot use for custom properties.
To empty or reset the value of a contact property, send a null value.

​
Headers

​
Idempotency-Key
string
Optionally send an idempotency key to avoid duplicate requests.
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.
The endpoint will return a 409 Conflict response if the idempotency key has been used in the previous 24 hours.

​
Response

​
Success

​
success
boolean
required

​
Error

If you send an idempotency key which has already been used in the previous 24 hours, a 409 Conflict response will be returned. All other errors will be 400 Bad Request.
​
success
boolean
required
​
message
string
required
An error message describing the problem with the request.
{
  "success": true
}
Last modified on October 15, 2025