> ## Documentation Index
> Fetch the complete documentation index at: https://docs.go.gbgplc.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Step 2: Start a journey

> Start a customer verification journey using the GBG GO API to create a trackable journey instance with assigned tasks.

Once you’ve authenticated and obtained an access token, the next step is to start a customer journey.

Starting a journey creates a journey instance that can be tracked, assigned tasks, and progressed using additional API calls.

<Note>
  Use the [`Start journey
          (/journey/start)`](/docs/go-v1/api-reference/endpoint/start-journey) endpoint to
  start a customer verification journey. Also, you must include a valid access
  token in your request to start a journey.
</Note>

## Prerequisites

* **A published journey** – A business user must create and publish the journey in the GBG GO platform.
* **Journey resource ID** – A unique identifier for the journey. You can use a specific version, for example, `@2z5wz848`, or the latest version, `@latest`.
* **Access token** – Obtained from the [Authenticate](/docs/go-v1/developer-integration/execute-customer-journeys/authenticate) step.

## Choose how to start the journey

There are two execution modes:

| Mode                 | Description                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
| -------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Prefill mode**     | You send customer data upfront in the request. The system might auto-complete matching tasks. By default, prefill mode operates synchronously, which means the `/journey/start` response returns only after processing is complete for all modules. You can also start a prefill journey in asynchronous mode, which means that the `/journey/start` call initiates the journey and return the instance ID and the processing happens asynchronously. Async prevents timeout issues with long-running processes. |
| **Non-prefill mode** | You start the journey without user data. Required details must be submitted via tasks later.                                                                                                                                                                                                                                                                                                                                                                                                                     |

Use prefill mode when you already have verified user data. Use non-prefill mode if the customer will provide their data during the journey.

<Note>
  In synchronous prefill execution, If module processing fails to complete, a `5xx` error is returned.
</Note>

### Start a journey (non-prefill mode)

If you're not including any user data, then send a request in the following format to the [`Start journey (/journey/start)`](/docs/go-v1/api-reference/endpoint/start-journey) endpoint:

```bash cURL theme={null}
curl --request POST \
  --url https://eu.platform.go.gbgplc.com/captain/api/journey/start \
  --header 'Authorization: Bearer your_access_token' \
  --header 'Content-Type: application/json' \
  --data '{
    "resourceId": "your-journey-resourceID@latest",
    "context": {
      "subject": {
        "documents": [],
        "biometrics": []
      }
    }
  }'
```

<Tip>
  Replace `@latest` with your specific journey version. For example: `"resourceId": "8c24f3a5b76d09e182c397fd45c91ae3f8b530d7a19e64c2bd93f5a76c48e09f@3x5wz848"`.

  Note that using `@latest` can have a small delay in processing.
</Tip>

#### What happens

* A journey instance is created.
* The response includes an `instanceId` which you'll use in later steps.
* All required tasks will need to be completed manually.

### Start a journey (prefill mode)

If you already have user data, then include it in the `context` object by sending a request to the same [`Start journey (/journey/start)`](/docs/go-v1/api-reference/endpoint/start-journey) endpoint. To know what and how to pass the user data, check the [User data schema](/docs/go-v1/api-reference/schema) reference. Depending on the user data you're passing, your request looks something like this:

```bash cURL theme={null}
curl --request POST \
  --url https://eu.platform.go.gbgplc.com/captain/api/journey/start \
  --header 'Authorization: Bearer your_access_token' \
  --header 'Content-Type: application/json' \
  --data '{
    "resourceId": "your-journey-resourceID@latest",
    "context": {
      "subject": {
        "identity": {
          "firstName": "Jane",
          "lastNames": ["Doe"],
          "dateOfBirth": "1992-10-01",
          "emails": [
            {
              "type": "work",
              "email": "jane.doe@example.com"
            }
          ]
        },
        "documents": [],
        "biometrics": []
      }
    }
  }'
```

<Note>
  The structure of the context object depends on the schema configured in the
  GBG GO platform. Always check the schema before sending data.
</Note>

### Start a journey (`async`: prefill mode)

To start a journey in asynchronous mode, include `"async": true` in the config object within your request context, as shown below:

```bash cURL theme={null}
curl --request POST \
  --url https://eu.platform.go.gbgplc.com/captain/api/journey/start \
  --header 'Authorization: Bearer your_access_token' \
  --header 'Content-Type: application/json' \
  --data '{
    "resourceId": "your-journey-resourceID@latest",
    "context": {
     "config": { "async": true},
      "subject": {
        "identity": {
          "firstName": "Jane",
          "lastNames": ["Doe"],
          "dateOfBirth": "1992-10-01",
          "emails": [
            {
              "type": "work",
              "email": "jane.doe@example.com"
            }
          ]
        },
        "documents": [],
        "biometrics": []
      }
    }
  }'
```

#### Get the schema

The schema defines the required fields, formats, and structure for customer data.
Refer to [User data schema](/docs/go-v1/api-reference/schema) for an explanation of the
schema for passing customer data.

To retrieve the schema for your journey:

1. Log in to the GBG GO platform.
2. Go to the **Journey Dashboard**.
3. Locate your journey.
4. Click **Schema**.

<Note>
  Providing data in the wrong structure will result in validation errors or
  incomplete journeys.
</Note>

#### What happens after starting a journey

Once a journey is successfully started:

* You’ll receive an `instanceId`.
* You can now fetch assigned tasks, retrieve schemas, and submit task data.
* If prefilled data was used, then some tasks may already be completed.

## Next step

Go to [Retrieve tasks](/docs/go-v1/developer-integration/execute-customer-journeys/retrieve-tasks-step) to get the list of tasks assigned to the journey.