---
title: "Update a contact property default"
method: PATCH
path: "/v1/contact-properties/{id}"
tags: ["Contacts"]
---

# Update a contact property default

`PATCH /v1/contact-properties/{id}`

## Request

- Base URL: `https://smtpfa.st/api`
- URL: `https://smtpfa.st/api/v1/contact-properties/{id}`
- Auth: HTTP bearer

Changes fallback_value only. Key and type are immutable: renaming would orphan the values already stored under the old key.

## Path parameters

- `id` string, required

## Request body

- object
  - `fallback_value` union, required: The new fallback; null clears it. key and type cannot change.
    - string
    - number

## Response `200`

The updated property

- object
  - `contact_property` ContactProperty, required
    - `id` string, required
    - `key` string, required
    - `type` 'string' | 'number', required
    - `fallback_value` union, required: Used when a contact has no value. A number for a number property; null when unset.
      - string
      - number
    - `created_at` string, date-time, required

## Other responses

- `400`: Invalid default, or an attempt to change key or type
- `404`: Not found

---

[API](https://skmtc.dev/smtpfa/apis/smtpfast-api.md) · [All operations](https://skmtc.dev/smtpfa/apis/smtpfast-api/llms.txt) · [OpenAPI document](https://skmtc.dev/smtpfa/apis/smtpfast-api/revisions/79dda742f53e?raw)