Response headers in Postman

Introduction

Response headers tell us important details about the server's reply to our request. They help us understand how the server handled our request.

Checking if the server sent the correct content type like JSON or HTML.

Verifying if the server set cookies or authentication tokens.

Confirming caching rules to see if data can be stored for faster loading.

Debugging why a request failed by looking at server messages in headers.

Ensuring security headers like CORS or HSTS are present.

Syntax

Postman

pm.response.headers.get('Header-Name')

Use the exact header name inside quotes to get its value.

Header names are case-insensitive but write them as they appear for clarity.

Examples

This gets the Content-Type header value and prints it.

Postman

let contentType = pm.response.headers.get('Content-Type');
console.log(contentType);

This fetches the Server header to know which server software responded.

Postman

let server = pm.response.headers.get('Server');
console.log(server);

This checks caching instructions from the server.

Postman

let cacheControl = pm.response.headers.get('Cache-Control');
console.log(cacheControl);

Sample Program

This test checks if the response header Content-Type exactly matches 'application/json'. If yes, the test passes; otherwise, it fails.

Postman

pm.test('Check Content-Type header is application/json', () => {
    let contentType = pm.response.headers.get('Content-Type');
    pm.expect(contentType).to.eql('application/json');
});

Important Notes

Headers can have multiple values separated by commas; get() returns the full string.

If a header is missing, get() returns null, so check for that to avoid errors.

Use Postman Console to see header values during test runs for easier debugging.

Summary

Response headers give extra info about the server's reply.

Use pm.response.headers.get('Header-Name') to read headers in Postman tests.

Check headers to verify content type, caching, security, and more.