# PATCH /contacts/{contact_id}/topics (Resend API)
Base URL: https://api.resend.com
Auth: Authorization: Bearer <RESEND_API_KEY>
Last verified: 2026-09-03

> Update topics for a contact

## Critical Gotchas
* All requests must include a `User-Agent` header (e.g. `User-Agent: my-app/1.0`) or the API returns HTTP 403.
* The `to` field is an array of strings, even when sending to a single recipient.

## cURL
curl -X PATCH 'https://api.resend.com/contacts/contact-id/topics' \
  -H "Authorization: Bearer $RESEND_API_KEY" \
  -H 'User-Agent: my-app/1.0' \
  -H 'Content-Type: application/json' \
  -d '{"topics":[{"id":"string","subscription":"opt_in"}]}'

## Parameters
| Name | In | Type | Required | Description |
| :--- | :--- | :--- | :--- | :--- |
| contact_id | path | string | Yes | The Contact ID or email address. |
| topics | body | object[] | Yes | Request body field topics. |

## Response (200 OK)
{"object":"contact_topics","contact_id":"string","topics":[{"id":"string","subscription":"opt_in"}]}

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