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

# Prolific Integration

> Recruit participants from Prolific and automatically capture their IDs in your experiment data.

Fusion integrates with **Prolific** through URL parameter pass-through. When a Prolific participant clicks through to your quest, their Prolific identifiers are automatically captured and included in your experiment data.

## How It Works

1. You set up a study on Prolific with your quest URL
2. Prolific appends participant identifiers to the URL as query parameters
3. Fusion captures **all URL query parameters** and passes them to your experiments
4. Experiment data is saved with the Prolific IDs in the metadata

## Prolific URL Parameters

Prolific appends three standard parameters to your study URL:

| Parameter      | Description                                |
| -------------- | ------------------------------------------ |
| `PROLIFIC_PID` | The participant's unique Prolific ID       |
| `STUDY_ID`     | Your Prolific study ID                     |
| `SESSION_ID`   | The session ID for this particular attempt |

## Setting Up a Prolific Study

### Step 1: Get Your Quest URL

1. Create and publish your quest on Fusion
2. Copy the quest's public URL (e.g., `https://usefusion.ai/quests/your-quest-guid/run`)

### Step 2: Configure Prolific

1. Create a new study on Prolific
2. Set the **study URL** to your quest URL with Prolific's parameter placeholders:

```
https://usefusion.ai/quests/your-quest-guid/run?PROLIFIC_PID={{%PROLIFIC_PID%}}&STUDY_ID={{%STUDY_ID%}}&SESSION_ID={{%SESSION_ID%}}
```

Prolific will replace the placeholders with actual values when participants click through.

### Step 3: Access Parameters in Your Experiment

URL parameters are injected into your experiment as global JavaScript variables. In your jsPsych code:

```javascript theme={null}
// Access Prolific IDs directly as global variables
const prolificPid = typeof PROLIFIC_PID !== 'undefined' ? PROLIFIC_PID : null;
const studyId = typeof STUDY_ID !== 'undefined' ? STUDY_ID : null;
const sessionId = typeof SESSION_ID !== 'undefined' ? SESSION_ID : null;

// Or access all URL params via the urlParams object
const allParams = typeof urlParams !== 'undefined' ? urlParams : {};
console.log(allParams.PROLIFIC_PID);

// Include in your data
const jsPsych = initJsPsych({
  on_finish: function() {
    const data = jsPsych.data.get().json();
    jatos.endStudy(data);
  }
});
```

<Info>
  All URL parameters with valid JavaScript identifier names are automatically set as `window` properties. You can also access them via the global `urlParams` object which contains all parameters. Each parameter value is limited to 10KB.
</Info>

## How Prolific Data Appears in Exports

When experiment data is saved, the URL parameters (including Prolific IDs) are included in the dataset metadata:

```json theme={null}
{
  "urlParams": {
    "PROLIFIC_PID": "5f1a2b3c4d5e6f",
    "STUDY_ID": "abc123def456",
    "SESSION_ID": "xyz789"
  }
}
```

This makes it easy to match experiment data back to participants in Prolific.

## Additional URL Parameters

You can append **any custom URL parameters** beyond the standard Prolific ones. They'll all be captured and passed through:

```
https://usefusion.ai/quests/guid/run?PROLIFIC_PID={{%PROLIFIC_PID%}}&condition=treatment&group=A
```

In this example, `condition` and `group` would also be available as global variables in your experiment.

## Tips

* Test your study URL by appending fake parameters and verifying they appear in the experiment
* Use [onboarding](/onboarding/overview) to collect informed consent before the experiment begins
* Prolific completion redirects are handled externally — add a final jsPsych trial with a "Return to Prolific" link using your Prolific completion URL
* See [Running a Study](/quests/running-a-study) for the full end-to-end workflow with Prolific