curl -X POST 'https://api.resend.com/contacts/contact-id/segments/segment-id' \
  -H "Authorization: Bearer $RESEND_API_KEY" \
  -H 'User-Agent: my-app/1.0'

# POST /contacts/{contact_id}/segments/{segment_id} (Resend API)
Base URL: https://api.resend.com
Auth: Authorization: Bearer <RESEND_API_KEY>
Last verified: 2026-10-20

> Add a contact to a segment

## Critical Gotchas
* All requests must include a `User-Agent` header (e.g. `User-Agent: my-app/1.0`) or the API returns HTTP 403.

## cURL
curl -X POST 'https://api.resend.com/contacts/contact-id/segments/segment-id' \
  -H "Authorization: Bearer $RESEND_API_KEY" \
  -H 'User-Agent: my-app/1.0'

## Parameters
| Name | In | Type | Required | Description |
| :--- | :--- | :--- | :--- | :--- |
| contact_id | path | string | Yes | The Contact ID or email address. |
| segment_id | path | string | Yes | The Segment ID. |

## Response (200 OK)
{"object":"contact_segment","contact_id":"string","segment_id":"string"}

---
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POST

POST /contacts/{contact_id}/segments/{segment_id} — Resend API

Resend API

Add a contact to a segment

Base URL: https://api.resend.com
Auth: Authorization: Bearer <RESEND_API_KEY>
Last verified: 2026-10-20 · upstream hash matched

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Critical gotchas

All requests must include a User-Agent header (e.g. User-Agent: my-app/1.0) or the API returns HTTP 403.

cURL

curl -X POST 'https://api.resend.com/contacts/contact-id/segments/segment-id' \  -H "Authorization: Bearer $RESEND_API_KEY" \  -H 'User-Agent: my-app/1.0'

Parameters

Name	In	Type	Required	Description
contact_id	path	string	Yes	The Contact ID or email address.
segment_id	path	string	Yes	The Segment ID.

Response 200 OK

{
  "object": "contact_segment",
  "contact_id": "string",
  "segment_id": "string"
}

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