Scripts

Pre-request scripts run before a request is sent. Use them to set variables, add headers, generate dynamic values, or prepare authentication tokens.

Scripts use the same Postman-compatible pm API as post-response scripts. They run in the official Postman Sandbox runtime.

Examples

Set an environment variable

pm.environment.set('timestamp', new Date().toISOString())

The variable is available in the request URL, headers, and body as {{timestamp}}, and in post-response scripts via pm.environment.get('timestamp').

Add a header

pm.request.headers.add({
  key: 'X-Request-Id',
  value: 'req-' + Date.now()
})

Set variables for post-response scripts

Variables set in a pre-request script persist into the post-response script for the same request.

pm.globals.set('requestStartTime', Date.now())

Then in the post-response script:

pm.test("Request completed quickly", () => {
  const start = pm.globals.get('requestStartTime')
  const duration = Date.now() - start
  pm.expect(duration).to.be.below(2000)
})

pm.request

The pm.request object represents the request that is about to be sent. Changes to headers and method are applied to the actual request.

Modifying headers

// Add a header
pm.request.headers.add({ key: 'X-Custom', value: 'value' })

// Remove a header
pm.request.headers.remove('X-Custom')

Modifying the method

pm.request.method = 'POST'

Adding Scripts to OpenAPI Documents

Add pre-request scripts to your OpenAPI description using the x-pre-request extension. Scripts can be set at the operation level, the document level, or both. When both are present, the document-level script runs first.

Operation level

openapi: 3.1.0
info:
  title: Example
  version: 1.0
paths:
  '/users':
    get:
      summary: Get all users
      x-pre-request: |-
        pm.environment.set('timestamp', new Date().toISOString())

Document level

openapi: 3.1.0
info:
  title: Example
  version: 1.0
x-pre-request: |-
  pm.request.headers.add({
    key: 'X-Request-Id',
    value: 'req-' + Date.now()
  })

See the OpenAPI extensions reference for more details.