Cypress App

fixture

Load a fixed set of data located in a file.

Syntax

cy.fixture(filePath)
cy.fixture(filePath, encoding)
cy.fixture(filePath, options)
cy.fixture(filePath, encoding, options)

Usage

Correct Usage

cy.fixture('users').as('usersJson') // load data from users.json
cy.fixture('logo.png').then((logo) => {
  // load data from logo.png
})

Arguments

filePath (String)

A path to a file within the fixturesFolder , which defaults to cypress/fixtures.

You can nest fixtures within folders and reference them by defining the path from the fixturesFolder:

cy.fixture('users/admin.json') // Get data from {fixturesFolder}/users/admin.json

encoding (String)

The encoding to be used when reading the file. The following encodings are supported:

• 'ascii'
• 'base64'
• 'binary'
• 'hex'
• 'latin1'
• 'utf8'
• 'utf-8'
• 'ucs2'
• 'ucs-2'
• 'utf16le'
• 'utf-16le'
• null

Using null explicitly will return the fixture as a Cypress.Buffer instance, regardless of file extension.

options (Object)

Pass in an options object to change the default behavior of cy.fixture().

Option	Default	Description
timeout	responseTimeout	Time to wait for cy.fixture() to resolve before timing out

Yields

• cy.fixture() yields the contents of the file. Formatting is determined by its file extension.
• The yielded subject is not updated if the contents change on disk.

Examples

JSON

Load a users.json fixture

cy.fixture('users.json').as('usersData')

Omit the fixture file's extension

When no extension is passed to cy.fixture(), Cypress will search for files with the specified name within the fixturesFolder (which defaults to cypress/fixtures) and resolve the first one.

cy.fixture('admin').as('adminJSON')

The example above would resolve in the following order:

1. cypress/fixtures/admin.json
2. cypress/fixtures/admin.js
3. cypress/fixtures/admin.coffee
4. cypress/fixtures/admin.html
5. cypress/fixtures/admin.txt
6. cypress/fixtures/admin.csv
7. cypress/fixtures/admin.png
8. cypress/fixtures/admin.jpg
9. cypress/fixtures/admin.jpeg
10. cypress/fixtures/admin.gif
11. cypress/fixtures/admin.tif
12. cypress/fixtures/admin.tiff
13. cypress/fixtures/admin.zip

Use import statement

If you are loading a JSON fixture, you can simply use the import statement and let the bundler load it:

// cypress/e2e/spec.cy.js
import user from '../fixtures/user.json'
it('loads the same object', () => {
  cy.fixture('user').then((userFixture) => {
    expect(user, 'the same data').to.deep.equal(userFixture)
  })
})

Images

Image fixtures are sent as base64 by default

cy.fixture('images/logo.png').then((logo) => {
  // logo will be encoded as base64
  // and should look something like this:
  // aIJKnwxydrB10NVWqhlmmC+ZiWs7otHotSAAAOw==...
})

Change encoding of Image fixture

cy.fixture('images/logo.png', null).then((logo) => {
  // logo will be read as a buffer
  // and should look something like this:
  // Buffer([0, 0, ...])
  expect(Cypress.Buffer.isBuffer(logo)).to.be.true
})

Playing MP3 file

cy.fixture('audio/sound.mp3', 'base64').then((mp3) => {
  const uri = 'data:audio/mp3;base64,' + mp3
  const audio = new Audio(uri)

  audio.play()
})

Accessing Fixture Data

Using .then() to access fixture data

cy.fixture('users').then((json) => {
  cy.intercept('GET', '/users/**', json)
})

Using fixtures to bootstrap data

info

Check out our example recipe using cy.fixture() to bootstrap data for our application.

Modifying fixture data before using it

You can modify fixture data directly before visiting a URL or mounting a component that makes a network request to that URL.

End-to-End Test

cy.fixture('user').then((user) => {
  user.firstName = 'Jane'
  cy.intercept('GET', '/users/1', user).as('getUser')
})

cy.visit('/users')
cy.wait('@getUser').then(({ request }) => {
  expect(request.body.firstName).to.eq('Jane')
})

Component Test

cy.fixture('user').then((user) => {
  user.firstName = 'Jane'
  cy.intercept('GET', '/users/1', user).as('getUser')
})

cy.mount(<Users />)
cy.wait('@getUser').then(({ request }) => {
  expect(request.body.firstName).to.eq('Jane')
})

Notes

Shortcuts

Using the fixture StaticResponse property

Fixtures can also be referenced directly without using the .fixture() command by using the special property fixture on the cy.intercept() StaticResponse object.

cy.intercept('GET', '/users/**', { fixture: 'users' })

Validation

Automated File Validation

Cypress automatically validates your fixtures. If your .json, .js, or .coffee files contain syntax errors, they will be shown in the Command Log.

Encoding

Default Encoding

Cypress automatically determines the encoding for the following file types:

• .json
• .js
• .coffee
• .html
• .txt
• .csv
• .png
• .jpg
• .jpeg
• .gif
• .tif
• .tiff
• .zip

For other types of files, they will be read as utf8 by default, unless specified in the second argument of cy.fixture(). You can specify null as the encoding in order to read the file as a Cypress.Buffer instance instead.

this context

If you store and access the fixture data using this test context object, make sure to use function () { ... } callbacks. Otherwise the test engine will NOT have this pointing at the test context.

describe('User page', () => {
  beforeEach(function () {
    // "this" points at the test context object
    cy.fixture('user').then((user) => {
      // "this" is still the test context object
      this.user = user
    })
  })

  // the test callback is in "function () { ... }" form
  it('has user', function () {
    // this.user exists
    expect(this.user.firstName).to.equal('Jane')
  })
})

Large Files

Memory and Transfer Constraints

cy.fixture() reads the entire file into memory and transfers its contents from the Cypress Node.js server process to the browser test runner over an internal WebSocket connection. There is no explicit file size limit in Cypress itself, but large files — especially binary files like .zip archives — can cause Cypress to crash or become unresponsive due to:

• Memory pressure: The complete file must fit in available RAM and is held in the fixture cache for the duration of the test run.
• WebSocket message size: File contents are sent as a single message over the internal socket. Payloads that approach or exceed 100 MB can exceed socket-level buffer limits.

As a practical guideline, avoid using cy.fixture() with files larger than a few megabytes. Smaller test fixtures (representative subsets of production data) are preferable wherever possible.

Uploading Large Files via a File Input

If your goal is to simulate a file upload through an <input type="file"> element, use .selectFile() with a path string rather than loading the fixture first and then setting the input manually:

// ✅ Preferred for file upload simulation
cy.get('input[type="file"]').selectFile('cypress/fixtures/large.zip')

Keeping Large File Operations Server-Side

For scenarios where you must work with large files but do not need to transfer their full contents to the browser (for example, verifying file metadata or invoking a server-side operation), use cy.task() to keep the operation in the Node.js context:

// cypress.config.js
const { defineConfig } = require('cypress')
const fs = require('fs')

module.exports = defineConfig({
  e2e: {
    setupNodeEvents(on, config) {
      on('task', {
        getFileSize(filePath) {
          const { size } = fs.statSync(filePath)
          return size
        },
      })
    },
  },
})

// in your test
cy.task('getFileSize', 'cypress/fixtures/large.zip').then((size) => {
  expect(size).to.be.greaterThan(0)
})

Loaded just once

Please keep in mind that fixture files are assumed to be unchanged during the test, and thus Cypress loads them just once. Even if you overwrite the fixture file itself, the already loaded fixture data remains the same.

If you wish to dynamically change the contents of a file during your tests, consider cy.readFile() instead.

For example, if you want to reply to a network request with different object, the following will not work:

// 🚨 DOES NOT WORK
cy.intercept('GET', '/todos/1', { fixture: 'todo' }).as('todo')
// application requests the /todos/1 resource
// the intercept replies with the object from todo.json file

cy.wait('@todo').then(() => {
  cy.writeFile('/cypress/fixtures/todo.json', { title: 'New data' })
})
// application requests the /todos/1 resource again
// the intercept replies with the originally loaded object
// from the todo.json file and NOT { "title": "New data" }

In this situation, avoid using the fixture file and instead respond to the network request with the object

// ✅ RESPOND WITH OBJECT
cy.fixture('todo.json').then((todo) => {
  cy.intercept('GET', '/todos/1', { body: todo }).as('todo')
  // application requests the /todos/1 resource
  // the intercept replies with the initial object

  cy.wait('@todo').then(() => {
    // modify the response object
    todo.title = 'New data'
    // and override the intercept
    cy.intercept('GET', '/todos/1', { body: todo })
  })
})

Rules

Requirements

• cy.fixture() requires being chained off of cy.

Assertions

• cy.fixture() will only run assertions you have chained once, and will not retry.

Timeouts

• cy.fixture() should never time out.

caution

Because cy.fixture() is asynchronous it is technically possible for there to be a timeout while talking to the internal Cypress automation APIs. But for practical purposes it should never happen.

Command Log

• cy.fixture() does not log in the Command Log

See also

• Guide: Variables and Aliases
• cy.intercept()
• .then()
• .readFile() for a similar command without caching and with builtin retryability
• .selectFile() for simulating file uploads, including with large files
• cy.task() for keeping large file operations in the Node.js context
• Recipe: Bootstrapping App Test Data