What Is Pre Request Script In Postman


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what is pre request script in postman

Postman, a widely used API development and testing tool, offers a powerful feature called pre-request scripts, which empowers developers and testers to automate requests and streamline their API testing workflows. In Postman, what is pre request script in postman in this pre-request script is a piece of JavaScript code that is executed before sending a request to an API endpoint.

In this blog post, we will explore the concept of pre-request scripts in Postman, their significance, and provide a practical code example to illustrate their usage.

API testing often involves repetitive tasks such as setting headers, handling authentication, and manipulating request data. Pre-request scripts in Postman provide a solution to automate these tasks by allowing developers to run custom code before sending API requests. This capability opens up a world of possibilities for enhancing automation, dynamic parameterization, and request customization.

To showcase the power of pre-request scripts, let’s consider a common use case where we need to include an authentication token in the request header.

Set up the Pre-request Script in Postman

// Pre-request script example in Postman

    url: 'https://api.example.com/auth',
    method: 'POST',
    body: {
        mode: 'raw',
        raw: JSON.stringify({
            username: 'your_username',
            password: 'your_password'
}, function (err, response) {
    if (err) {

    var token = response.json().token;

    // Set the token in the request header
        key: 'Authorization',
        value: 'Bearer ' + token

By leveraging pre-request scripts, developers can automate various tasks, such as fetching dynamic values from external sources, manipulating request payloads, or configuring request headers based on environmental variables. This not only saves time but also improves the efficiency and accuracy of API testing.

PHP/cURL Code to Retrieve and Display Data

Now, let’s see how we can retrieve and display the data in PHP using cURL. Assuming you have PHP installed, create a new PHP file (e.g., retrieve_data.php) and add the following code:


$apiEndpoint = 'https://api.example.com/data'; // The API endpoint to retrieve data

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $apiEndpoint);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, array(
    'Content-Type: application/json',
    'Authorization: Bearer {your_token}' // Replace {your_token} with the actual token value

$response = curl_exec($ch);

// Display the retrieved data
echo $response;

Make sure to replace {your_token} in the PHP code with the actual token value obtained from the Pre-request Script in Postman.

By running the PHP script, you should be able to retrieve and display the data from the API endpoint, authenticated using the token set in the pre-request script.

Relative Blogs : Understanding The Upgrade-Insecure-Requests HTTP Header

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