Is there a programmatic way to change user agent in Cypress.io?

Question

I have some ad calls that are only made on mobile devices. In Chrome, I can use Device Mode and simulate a mobile device, and the resulting ad call from the server is correctly tailored to mobile. I'm not sure how Chrome does this, except possibly by sending a different user agent.

In the Cypress.io documentation, it says the user agent can be changed in the configuration file (Cypress.json). But, I need to run a test for a desktop viewport and then a mobile viewport with a mobile user agent. Is there a way to change the user agent programmatically?

Answer 1

Update: According to https://github.com/cypress-io/cypress/issues/3873 it is possible since Cypress 3.3.0 use user-agent property in a cy.request() and cy.visit().

If you need, for example, set userAgent as Googlebot:

cy.visit(url, {
    headers: {
        'user-agent': 'Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)',
    }
});

---

Original answer before Cypress 3.3.0

before(() => {
    cy.visit(url, {
        onBeforeLoad: win => {
            Object.defineProperty(win.navigator, 'userAgent', {
                value: 'Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)',
            });
        },
    });
});

Answer 2

Now cypress supports passing user agent in the header for cy.visit as well as cy.request:

it('Verify Social Sharing Meta Tags', () => {
  cy.visit(portalURL + '/whats_new/140', {
    headers: {
      'user-agent': 'LinkedInBot/1.0 (compatible; Mozilla/5.0; Apache-HttpClient +http://www.linkedin.com)',
    }
  });

  cy.document().get('head meta[name="og:type"]')
    .should('have.attr', 'content', 'website');
});

https://on.cypress.io/changelog#3-3-0

Update as on Aug 12, 2021:

• It seems you can't change the user agent anymore, reference https://docs.cypress.io/api/cypress-api/config#Notes

Answer 3

The other answers do not set the User-Agent header of the underlying HTTP request, just the userAgent property of win.navigator. To set the User-Agent header to a custom value for all HTTP requests, you can set the userAgent configuration option:

{
  // rest of your cypress.json...
  "userAgent": "Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)"
}