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PUT
/
v1
/
contacts
/
update
Update contact
curl --request PUT \
  --url https://app.loops.so/api/v1/contacts/update \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "email": "<string>",
  "userId": "<string>",
  "firstName": "<string>",
  "lastName": "<string>",
  "source": "<string>",
  "subscribed": true,
  "userGroup": "<string>",
  "mailingLists": {}
}
'
{
  "success": true,
  "id": "id_of_contact"
}
Update an existing contact by sending a request containing contact properties. This endpoint will create a contact if a matching contact does not already exist in your audience.
If you want to update a contact’s email address, the contact will first need a userId value. You can then make a request containing the userId field along with an updated email address.

​
Request

​
Body

Provide either email or userId to identify the contact you want to update.
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. If there is no contact with this email, one will be created.
Required if userId is not provided.
​
userId
string
A unique user ID (for example, from an external application). Read more Required if email is not provided.
​
firstName
string
The contact’s first name.
​
lastName
string
The contact’s last name.
​
source
string
A custom source value to replace the default “API”. Read more
​
subscribed
boolean
Whether the contact will receive campaign and loops emails. Read more.
If you send subscribed: true in your update calls, contacts who have previously unsubscribed will be re-subscribed. We recommend leaving this field out of your requests unless you specifically want to unsubscribe or re-subscribe a contact.
​
userGroup
string
You can use groups to segment users when sending emails. Currently, a contact can only be in one user group. Read more
​
mailingLists
object
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. Read more
"mailingLists": {
  "cm06f5v0e45nf0ml5754o9cix": true,
  "cm16k73gq014h0mmj5b6jdi9r": false
}

​
Custom properties

You can also include custom contact properties in your request body. These should be added as top-level attributes in the request. Custom properties can be of type string, number, boolean or date (see allowed date formats). 
{
  "email": "hello@gmail.com",
  "plan": "pro" /* Custom property */,
  "favoriteColor": "Blue" /* Custom 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.

​
Response

​
Success

​
success
boolean
required
​
id
string
required
The internal ID of the contact.

​
Error

Errors will be 400 Bad Request.
​
success
boolean
required
​
message
string
required
An error message describing the problem with the request.
{
  "success": true,
  "id": "id_of_contact"
}
Last modified on April 14, 2026