curl -X PATCH 'https://api.resend.com/domains/domain-id' \
  -H "Authorization: Bearer $RESEND_API_KEY" \
  -H 'User-Agent: my-app/1.0' \
  -H 'Content-Type: application/json' \
  -d '{
  "open_tracking": true,
  "click_tracking": true,
  "tls": "opportunistic",
  "capabilities": {
    "sending": "enabled",
    "receiving": "enabled"
  },
  "tracking_subdomain": "string"
}'

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

> Update an existing domain

## 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/domains/domain-id' \
  -H "Authorization: Bearer $RESEND_API_KEY" \
  -H 'User-Agent: my-app/1.0' \
  -H 'Content-Type: application/json' \
  -d '{"open_tracking":true,"click_tracking":true}'

## Parameters
| Name | In | Type | Required | Description |
| :--- | :--- | :--- | :--- | :--- |
| domain_id | path | string | Yes | The ID of the domain. |
| open_tracking | body | boolean | No | Track the open rate of each email. |
| click_tracking | body | boolean | No | Track clicks within the body of each HTML email. |
| tls | body | string | No | enforced \| opportunistic. |

## Response (200 OK)
{"id":"d91cd9bd-1176-453e-8fc1-35364d380206","object":"domain"}

---
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PATCH

/domains/{domain_id}

Resend API

Update an existing domain

Base URL: https://api.resend.com
Auth: Authorization: Bearer <RESEND_API_KEY>
Last verified: 2026-09-03 · upstream hash matched

Actions

Agents: curl -H "Accept: text/markdown" this URL
→ 234 tokens · Vary: Accept

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/domains/domain-id' \  -H "Authorization: Bearer $RESEND_API_KEY" \  -H 'User-Agent: my-app/1.0' \  -H 'Content-Type: application/json' \  -d '{  "open_tracking": true,  "click_tracking": true,  "tls": "opportunistic",  "capabilities": {    "sending": "enabled",    "receiving": "enabled"  },  "tracking_subdomain": "string"}'

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Parameters

Name	In	Type	Required	Description
domain_id	path	string	Yes	The ID of the domain.
open_tracking	body	boolean	No	Track the open rate of each email.
click_tracking	body	boolean	No	Track clicks within the body of each HTML email.
tls	body	string	No	enforced \| opportunistic.
capabilities	body	object	No	Configure the domain capabilities for sending and receiving emails. At least one capability must be enabled.
tracking_subdomain	body	string	No	The subdomain to use for click and open tracking.

Response 200 OK

{
  "id": "d91cd9bd-1176-453e-8fc1-35364d380206",
  "object": "domain"
}