Mirage JS
Mirage JS is a free, open-source JavaScript library for mocking backend APIs during frontend development and testing.
What Mirage JS is
Mirage JS is a free, open-source JavaScript library for mocking backend APIs during frontend development and testing. It runs in the browser, intercepting XMLHttpRequest and fetch requests so an application receives responses from a simulated service. An in-memory database, factories, fixtures, models, relationships, routes, and serializers help create records, lists, and changing backend states. Route handlers support every HTTP verb, delayed responses, and custom errors, allowing UI checks for empty data, failures, and slow replies. Mirage works in JavaScript applications built with React, Vue, and Angular, and guides cover Cypress, React Testing Library, and Vue Test Utils. Development and test use are supported; the test environment turns off delays and logging and ignores development seeds. Installation instructions include npm and Yarn. Teams can run a local offline frontend or share a prototype without backend services. Mirage supports REST and GraphQL, but browser-like environments such as jsdom are required for Node use.
Good
- Free and open source
- Mocks REST and GraphQL APIs
- Dynamic data with in-memory database
- Supports delayed and custom error responses
- Works offline without backend services
Watch out
- Runs in the browser
- Node requires a browser-like environment
- Not intended for production builds except prototypes
Who it suits
Mirage JS suits frontend developers and testers building JavaScript applications who need controllable API responses. It is useful for React, Vue, Angular, Cypress, and related testing workflows.
Verdict
Mirage JS provides a structured way to simulate backend behavior during development and testing. Its data tools, route controls, and framework guides fit teams that need repeatable API states without a running backend.
The facts
Each one read from Mirage JS's own pages, with the date it was checked.
What it does
- Development and testing
- Mirage can be used in both development and testing to simulate server data and scenarios.checked 7 Oct 2026
- Dynamic data
- It includes an in-memory database and helper functions for simulating dynamic backend services.checked 7 Oct 2026
- Framework integrations
- The standalone library is used in JavaScript apps built with React, Vue, and Angular.checked 7 Oct 2026
- Frameworks
- The maker says Mirage works with all major JavaScript frameworks, libraries, and test runners; its about page names React, Vue, and Angular apps.checked 7 Oct 2026
- HTTP behavior
- Route handlers support all HTTP verbs, simulated response timing, and custom error responses.checked 7 Oct 2026
- Installation
- The installation guide provides npm and Yarn commands and directs users to quickstarts for their stack.checked 7 Oct 2026
- Integrations
- Official guides cover Cypress and React Testing Library.checked 7 Oct 2026
- License
- The GitHub repository identifies Mirage JS as MIT licensed.checked 7 Oct 2026
- Mock data
- Its in-memory database and factories can create records and lists for development and tests.checked 7 Oct 2026
- Offline development
- The maker says collaborators can install the frontend project and use a local offline development environment without environment variables or auth tokens.checked 7 Oct 2026
- Pricing and security
- The official documentation pages opened describe installation and library usage but do not state product pricing, trial terms, or security certifications.checked 7 Oct 2026
- Production use
- The application testing guide recommends excluding Mirage from production builds unless it is being used to build a prototype.checked 7 Oct 2026
- Prototype sharing
- Mirage can mock an entire API so teams can share a working JavaScript prototype without running backend services.checked 7 Oct 2026
- Purpose
- Mirage JS is a client-side API mocking library for building, testing, and sharing JavaScript applications without relying on backend services.checked 7 Oct 2026
- Request interception
- It runs in the browser and intercepts XMLHttpRequest and fetch requests so apps can receive mocked responses.checked 7 Oct 2026
- Runtime limit
- The maker says Mirage runs in Node only in a browser-like environment such as jsdom, and cannot mock a React app's server-side API requests.checked 7 Oct 2026
- Server features
- Its conventions include routes, a database, models and relationships, factories, fixtures, and serializers.checked 7 Oct 2026
- Support
- The official site links to GitHub, Discord, and Twitter for community access.checked 7 Oct 2026
- Support resources
- The documentation site provides guides, a tutorial, API reference, quickstarts, and a REPL.checked 7 Oct 2026
- Testing integrations
- Official guides show Mirage working with Cypress, React Testing Library, and Vue Test Utils.checked 7 Oct 2026
- UI testing
- Mirage supports high-level UI tests against different API states, including empty data, errors, and slow responses.checked 7 Oct 2026
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