Developers, QA engineers, and testers often find themselves in a tricky spot waiting for an API to be built, dealing with inconsistent responses, or trying to test how an app handles errors. Instead of relying on backend changes or waiting on fixes, Overriding API response lets you take control by modifying responses on the fly.

Why Override API Responses?

Whether you’re debugging, testing, or speeding up development, overriding API responses can make your life easier. Here’s why it’s useful:

• Work Without Backend Dependencies – Simulate API responses even if the backend isn’t ready or is unreliable.
• Test Edge Cases and Errors – Manually trigger error codes and unexpected data formats to ensure your app handles them correctly.
• Speed Up Development – Use mock data to keep building your frontend without being blocked by backend delays.
• Ensure Consistent Testing – Remove variability by controlling API responses, so you always test under the same conditions.

With the right Chrome extensions that let you modify responses dynamically you can test and develop with complete flexibility, without waiting on backend changes.

Requestly

4.3 (1.2k ratings)

Requestly is an open-source Chrome extension that enables developers to modify API responses directly, making it easy to test unusual response scenarios without backend changes. It provides an intuitive interface to override API responses dynamically, helping in debugging, testing, and development workflows.

Key Features

• Modify API responses statically and dynamically.
• Share response modification rules with your team using **workspaces.**
• Supports both REST and GraphQL APIs.
• Apply advanced filtering based on Request Method.
• Modify headers, redirect requests, inject scripts, and block network calls.

Pros

• Powerful and flexible, perfect for developers and power users.
• Supports complex API response modification scenarios.
• Active community and support.
• MV3 supported

Cons

• Free version limits some premium features.

Tweak

4.7 (203 ratings)

Tweaks is a lightweight Chrome extension designed to modify API responses on the go. It allows developers to edit response payloads in real-time, making debugging and front-end testing more efficient.

Key Features

• Intercept and modify API responses.
• Supports JSON response manipulation.
• Simple UI with quick toggles.

Pros

• Easy to set up and use.
• Great for quick API modifications.
• No complex configurations needed

Cons

• Limited to basic API response changes
• Free version limits some premium features.

ModHeader

3.2 (1.1k ratings)

ModHeader primarily focuses on modifying HTTP headers, but its Mod Response feature extends its capabilities to API response manipulation. Users can alter response payloads, modify status codes, and adjust response headers dynamically. This makes it particularly useful for testing authentication headers, CORS policies, error handling scenarios, and custom response payloads without backend modifications

Note: ModHeader includes ads, which may disrupt the user experience

Key Features

• Modifies request and response headers alongside redirects.
• Offers filters to target specific tabs or domains.
• Supports rule export/import for sharing.

Pros

• Combines API response modification with redirection and header adjustments.
• Responsive and efficient for testing purposes.

Cons

• Advanced features are paywalled, limiting full access.
• Less intuitive for non-technical users.
• Less focus on full API response overriding

Mokku

3.4 (77 ratings)

Mokku is a Chrome extension that integrates seamlessly into the Developer Tools, allowing developers to mock and modify API responses directly within the browser. It’s particularly useful for testing various scenarios without relying on backend changes.

NoteMokku includes ads, which may disrupt the user experience

Key Features

• Dynamic API mocking to intercept and modify responses including status codes, headers, and payloads.
• A dedicated DevTools tab for easy management of mocks.
• Customizable response parameters for simulating different response times, error states, and data structures.

Pros

• Ideal for front-end testing without relying on backend dependencies.
• Enables real-time API response modifications.
• Facilitates testing of edge cases and error handling.

Cons

• Requires manual setup for each API endpoint to be mocked.
• Might not support certain response types, such as markdown files.

Conclusion

Requestly is the clear winner. It’s open-source, has the best UI, and does way more than just Overriding API Responses. From modifying headers to injecting scripts, it’s built for developers who need flexibility.