---
title: "Send a transactional in-app message"
method: POST
path: "/v1/send/in_app"
tags: ["Send Messages"]
---

# Send a transactional in-app message

`POST /v1/send/in_app`

Send a transactional in-app message. In-app messages render in your application through the Customer.io SDK to the devices associated with the person you target by `identifiers`.

You send a message using a `transactional_message_id` for an in-app message template that you've set up in the user interface. The `transactional_message_id` can be either the numerical ID for the template or the *Trigger Name* that you assigned the template.

You can find your `transactional_message_id` from the code sample in the **Overview** tab for your transactional message in the user interface, or you can look up a list of your transactional messages through the [App API](/integrations/api/app/tag/transactional/).

**Note**: Your workspace must have in-app messaging enabled. Requests sent to a workspace without the in-app capability return `403`.

## Headers

- `X-Workspace-Id` integer

## Request body

- Sendinapp
  - `transactional_message_id` union, required — The transactional message template that you want to use for your message. You can call the template by its numerical ID or by the *Trigger Name* that you assigned to the template in the UI (case insensitive).
    - integer — The ID of the transactional message you want to send.
    - string — The name of trigger for the transactional message you want to send; you set the trigger name in the *Configure Settings* step when setting up your message. This is case insensitive.
  - `identifiers` union, required — Identifies the person represented by your transactional message by one of, and only one of, `id`, `email`, or `cio_id`.
    - object
      - `id` string, required — The identifier for the person represented by the transactional message. **NOTE**: If your workspace identifies people by email, use the `email` identifier instead.
    - object
      - `email` string, required — The identifier for the person represented by the transactional message. Use this option if your workspace identifies people by email rather than by `id`.
    - object
      - `cio_id` string, required — A unique, immutable identifier for a person, set by Customer.io when you add a person.
  - `message_data` object — An object containing the key-value pairs referenced using liquid in the format `{{trigger.<property_name>}}` in your in-app message. These values populate the `properties` field in the message that the SDK delivers to your application.
  - `send_at` integer — A unix timestamp (seconds since epoch) determining when the message will be sent. The timestamp can be up to 90 days in the future. If this value is in the past, your message is sent immediately.
  - `queue_draft` boolean — If true, your transactional message is held as a draft in Customer.io and not sent directly to your audience. You must go to the Deliveries and Drafts page to send your message.
  - `language` string — Overrides language preferences for the person you want to send your transactional message to. Use one of our [supported two- or four-letter language codes](/journeys/channels/localization/getting-started/#supported-languages).
  - `auto_create` boolean — Accepted for in-app sends, but of limited use. An auto-created record has no content or layout until you populate it in the UI, so we recommend [creating the in-app message in the UI](/journeys/send/transactional/in-app/) instead. Your `transactional_message_id` must be a new string.

## Response `200`

Returns a unique ID for the delivery.

- object
  - `delivery_id` string — A unique identifier for the message.
  - `queued_at` integer — A Unix timestamp for when Customer.io accepted and queued your request. For scheduled messages (using `send_at`), this is when we received your request, not when the message sends.
  - `send_at` integer — For a scheduled message, the Unix timestamp when the message is set to send. Returned only when you provide a future `send_at`.

## Other responses

- `400` — The request was malformed.
- `403` — Your workspace is not authorized for transactional messaging or in-app messages.

---

[API](https://skmtc.dev/customer/apis/customer-io-journeys-api-reference.md) · [All operations](https://skmtc.dev/customer/apis/customer-io-journeys-api-reference/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/customer/customer-io-journeys-api-reference/revisions/4b391af7cb06/schema)