This API enables you to append values to list type properties of your users listed in your User Profiles. If the user with distinct ID doesn't exist, it creates a new user with the provided distinct ID and updates values for all the provided properties.

Note: If a property was not created earlier, it will create a new property and the data type of the property will set to List. For example, if you $append a new property called order_ids=245, it will create the order_ids property with List type and value [245]. A list may contain only unique values, so if a value already exists, and you try to add the same value, it will be ignored.

You can append values with the following data types:

• String: Can be alphanumeric and contain a maximum of 255 characters. Example: products_order=['iPhone 16 Pro', 'iPad 32 GB'].
• Number: Can be an integer or a decimal. Example: purchase_amount=[23000, 20.34].
• Date: Must be in ISO 8601 format: YYYY-MM-DDTHH:MM:SS.sssZ. Example: membership_date=2020-10-01T18:30:00.000Z or membership_date=2020-10-01T18:30:00Z or membership_date=2020-10-01T18:30:00.000+05:30 or membership_date=2020-10-01T18:30:00+02:00 or membership_date=2020-10-01.

You can append only one value to a property at a time. Although not recommended, a list property can contain a mix of different data types.

These user properties can be used to filter your users for creating user cohorts and campaigns.

{
  "$append": {
    "property_1": "some text",
    "property_2": 123,
    "property_3": 45.67,
    "property_4": "2020-10-01T18:30:00.000Z",
    "property_5": "2021-12-01",
    "property_n": "2021-11-01T13:35:00+02:00"
  },
  "distinct_id": "XXXXXXXX"
}

{
  "request_id": "XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX"
}