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Mock the response of a request. You can define a mock based on a matching glob and corresponding header and status code. Calling the mock method returns a stub object that you can use to modify the response of the web resource.

With the stub object you can then either return a custom response or have the request fail.

There are 3 ways to modify the response:

  • return a custom JSON object (for stubbing API request)
  • replace web resource with a local file (service a modified JavaScript file) or
  • redirect resource to a different url

Note that using the mock command requires support for Chrome DevTools protocol. That support is given if you run tests locally in Chromium based browser or if you use a Selenium Grid v4 or higher. This command can not be used when running automated tests in the cloud. Find out more in the Automation Protocols section.

browser.mock(url, { method, headers, responseHeaders, postData, statusCode })
urlString, RegExpurl to mock
MockFilterOptionsfilter mock resource by additional options
filterOptions.methodString, Functionfilter resource by HTTP method
filterOptions.headersObject, Functionfilter resource by specific request headers
filterOptions.responseHeadersObject, Functionfilter resource by specific response headers
filterOptions.postDataString, Functionfilter resource by request postData
filterOptions.statusCodeNumber, Functionfilter resource by response statusCode
it('should mock network resources', async () => {
// via static string
const userListMock = await browser.mock('**' + '/users/list')
// or as regular expression
const userListMock = await browser.mock(/https:\/\/(domainA|domainB)\.com\/.+/)
// you can also specifying the mock even more by filtering resources
// by request or response headers, status code, postData, e.g. mock only responses with specific
// header set and statusCode
const strictMock = await browser.mock('**', {
// mock all json responses
statusCode: 200,
headers: { 'Content-Type': 'application/json' },
responseHeaders: { 'Cache-Control': 'no-cache' },
postData: 'foobar'

// comparator function
const apiV1Mock = await browser.mock('**' + '/api/v1', {
statusCode: (statusCode) => statusCode >= 200 && statusCode <= 203,
headers: (headers) => headers['Authorization'] && headers['Authorization'].startsWith('Bearer '),
responseHeaders: (headers) => headers['Impersonation'],
postData: (data) => typeof data === 'string' && data.includes('foo')

it('should modify API responses', async () => {
// filter by method
const todoMock = await browser.mock('**' + '/todos', {
method: 'get'

// mock an endpoint with a fixed fixture
title: 'Injected Todo',
order: null,
completed: false,
url: ""

// respond with different status code or header
title: 'Injected Todo',
order: null,
completed: false,
url: ""
}], {
statusCode: 404,
headers: {
'x-custom-header': 'foobar'

it('should modify text assets', async () => {
const scriptMock = await browser.mock('**' + '/script.min.js')

it('should redirect web resources', async () => {
const headerMock = await browser.mock('**' + '/header.png')

const pageMock = await browser.mock('')
await browser.url('')
console.log(await browser.getTitle()) // returns "WebdriverIO · Next-gen browser and mobile automation test framework for Node.js"

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