Generate data for a Postman request

Created: 24 November 2020

Updated: 03 September 2023

When making requests with Postman to test an API it is often useful to have generated data, for example when creating users in a backend system you may want the ability to get custom user data

The method we will use to do this is by setting Postman environment variables in the Pre-request Script of a Postman request

Firstly, we can write some basic logging in the Pre-request script section on Postman and view the result in the Postman console:

const name = 'Nabeel'

console.log(`Hello ${name}`)

Additionally, postman gives us some functions to set and get environment variables, so we can set the name as an environment variable like so:

const name = 'Nabeel'

pm.environment.set('name', name)

And log it like so:


Aditionally, we can make HTTP Requests using pm.sendRequest which then takes a callback for what we want to do after the request, we can use the randomuser api to get a user:

pm.sendRequest('', (err, res) => {
  const apiResponse = res.json()

  // do more stuff

Using this method, we can get some random user data and set it in the environment variables as follows:

pm.sendRequest('', (err, res) => {
  const apiResponse = res.json()

  const user = apiResponse.results[0]

  const email =
  const firstName =
  const lastName =

  pm.environment.set('email', email)
  pm.environment.set('firstName', firstName)
  pm.environment.set('lastName', lastName)

We can then use this in our request body using Postman’s {\{}\} syntax. If we were making a JSON request, our body would look something like this:


  "email": "{{email}}",
  "firstName": "{{firstName}}",
  "lastName": "{{lastName}}"

Postman will then populate the slots from the environment variables that we set automatically when making the request