# 0 (Heartbeat)

The **`0` (Heartbeat)** message is used to verify that a connection between two parties is still active.

| Tag       | Name          | Type       | Required                                    | Description                                                                                                                                                                                                                                                                                  |
| --------- | ------------- | ---------- | ------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **112**   | `TestReqID`   | `String`   | **no**                                      | Always provided by Revolut FIX Gateway when the heartbeat is the result of the [**`1` (Test Request)**](/docs/guides/exchange-fix-api/trading-fix-api/supported-fix-messages/fix-session-level-messages/message-1-test-request). In that case, the same `TestReqID` identifier will be used. |

For a sample message and other details, see [`FIX 4.4 : Heartbeat <0> message` in the FIX 4.4 documentation](https://www.onixs.biz/fix-dictionary/4.4/msgtype_0_0.html).