API Mock Generator

What is an API mock generator?

An API mock generator helps you design a fake HTTP response—status, headers, and JSON—so frontend and test code can run before a backend exists. This page builds that response in your browser and exports JSON, MSW, and Express snippets. It does not host a public URL.

Use this generator to design and export mock responses. Use MSW, Express, or a hosted mock server when something must actually answer HTTP requests.

Quick answers

Concise answers for common searches — definitions, steps, and comparisons.

How to generate a mock API response

1. 1

   Choose method and route

   Pick GET, POST, PUT, PATCH, or DELETE and enter a path such as /api/users or /api/users/1.

2. 2

   Set status and delay

   Use 200 or 201 for success, 204 for an empty body, and 4xx/5xx for errors. Set delay in milliseconds to simulate latency for loading states.

3. 3

   Add headers and JSON

   Keep Content-Type: application/json for typical REST mocks. Paste the response body, then format or fix JSON until validation passes. Leave the body empty for 204.

4. 4

   Preview and export

   Check the local HTTP preview, then copy JSON config, an MSW handler, or an Express route. Fetch and cURL tabs are request examples only—not hosted endpoints.

API Mock Generator examples

GET /api/users/1 · status 200 · delay 120ms

{ "id": 1, "name": "Ada Lovelace", "email": "ada@example.com" }

POST /api/users · status 201 · Location: /api/users/42

{ "id": 42, "name": "Ada Lovelace", "email": "ada@example.com" }

GET /api/users · status 200

{ "data": [...], "pagination": { "page": 1, "limit": 10, "total": 42, "pages": 5 } }

GET /api/users/999 · status 404

{ "error": "Not found", "message": "No user exists with that id." }

Same 200 mock → MSW handler tab

http.get('*/api/users/1', async () => { await delay(120); return HttpResponse.json(...) })

Mock JSON, errors, and latency

Use the mock with Express and MSW

Common mistakes to avoid

When this tool isn't the right choice

When to use API Mock Generator vs related tools

Format and validate JSON on those pages. Come back here when the payload needs an HTTP envelope and export snippets.

What to do next

Continue the workflow with the right follow-up tool.

• Need to clean the response body first? Open the JSON Formatter .
• Syntax errors in the payload? Check them with the JSON Validator .
• Infer a contract from sample JSON using the JSON Schema Generator .
• Draft extra response headers with the HTTP Header Generator .
• Need CORS on a local stub? Use the CORS Header Generator .
• Turning a captured request into fetch()? Try cURL to Fetch .
• Mocking authenticated routes? Generate a placeholder secret with the API Key Generator .

Frequently asked questions

Privacy, accuracy, and trust

Not a hosted mock API, API gateway, or OpenAPI mock server. You remain responsible for how exported mocks are used.