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

# Update a contact property

`PATCH /contact-properties/{id}`

## Request

- Base URL: `https://api.eusend.dev`
- URL: `https://api.eusend.dev/contact-properties/{id}`
- Auth: HTTP bearer

Only the fallback value can change. Renaming or retyping a property would have to rewrite every contact and every broadcast body spelling `{{old_key}}`, so both are a delete and a create.

## Path parameters

- `id` string, uuid, required

## Request body

- UpdateContactPropertyRequest
  - `fallback_value` string, nullable, required: The only mutable field. Send `null` to clear the fallback.

## Response `200`

Updated.

- ContactProperty
  - `id` string, uuid, required
  - `key` string, required
  - `type` 'string' | 'number', required
  - `fallbackValue` string, nullable, required: Substituted into `{{key}}` for contacts carrying no value of their own. `null` renders empty.
  - `createdAt` string, date-time, required
  - `updatedAt` string, date-time, nullable

## Other responses

- `400`: The request body or query failed validation (`VALIDATION_ERROR`).
- `401`: Missing, malformed, or revoked API key (`UNAUTHORIZED`).
- `403`: The key exists but may not reach this resource — a `sending_access` key outside the send paths, a test-mode key writing live state, or an account on hold (`FORBIDDEN`, `ACCOUNT_RESTRICTED`).
- `404`: No such resource on this organization (`NOT_FOUND`).
- `429`: Rate limit exceeded (`RATE_LIMITED`).
- `500`: Unexpected server error (`INTERNAL_ERROR`). Carries `request_id`.

---

[API](https://skmtc.dev/eusend/apis/eusend-api.md) · [All operations](https://skmtc.dev/eusend/apis/eusend-api/llms.txt) · [OpenAPI document](https://skmtc.dev/eusend/apis/eusend-api/revisions/bec561f55488?raw)