---
title: "Upsert up to 1,000 contacts"
method: POST
path: "/audiences/{id}/contacts/batch"
tags: ["Contacts"]
---

# Upsert up to 1,000 contacts

`POST /audiences/{id}/contacts/batch`

## Request

- Base URL: `https://api.eusend.dev`
- URL: `https://api.eusend.dev/audiences/{id}/contacts/batch`
- Auth: HTTP bearer

For importing a list. Addresses are lowercased and de-duplicated server-side. An import can add an opt-out but never remove one.

## Path parameters

- `id` string, uuid, required

## Request body

- BatchContactsRequest
  - `contacts` object[], required
    - `email` string, email, required
    - `first_name` string
    - `last_name` string
    - `unsubscribed` boolean: Carries an opt-out over from another provider. An import can only ever add an opt-out — `false` will not resubscribe someone.
    - `created_at` string, date-time: Original signup time. Applied on insert only.
    - `properties` object: Custom properties, usable as `{{key}}` in a broadcast body. Unlike the single-contact endpoint, an import MERGES these into whatever the contact already has, so a CSV carrying only `plan` will not drop a `company` an earlier import set.

## Response `201`

Imported.

- BatchContactsResponse
  - `count` integer, required: Rows written.
  - `duplicates` integer, required: Repeated addresses collapsed before the write.

## Other responses

- `400`: The request body or query failed validation (`VALIDATION_ERROR`).
- `401`: Missing, malformed, or revoked API key (`UNAUTHORIZED`).
- `403`: The import would exceed the plan contact limit (`PLAN_LIMIT_EXCEEDED`).
- `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)