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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.

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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

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Prolific URL Parameters

Prolific appends three standard parameters to your study URL:
ParameterDescription
PROLIFIC_PIDThe participant’s unique Prolific ID
STUDY_IDYour Prolific study ID
SESSION_IDThe session ID for this particular attempt

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Setting Up a Prolific Study

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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)

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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.

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Step 3: Access Parameters in Your Experiment

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

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How Prolific Data Appears in Exports

When experiment data is saved, the URL parameters (including Prolific IDs) are included in the dataset metadata: 
{
  "urlParams": {
    "PROLIFIC_PID": "5f1a2b3c4d5e6f",
    "STUDY_ID": "abc123def456",
    "SESSION_ID": "xyz789"
  }
}
This makes it easy to match experiment data back to participants in Prolific.

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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.

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Tips

  • Test your study URL by appending fake parameters and verifying they appear in the experiment
  • Use onboarding 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 for the full end-to-end workflow with Prolific