Intercept & modify API responses on the fly

Test edge cases in your app by simulating API responses‍.

Override XHR/fetch Response

Using Requestly Modify Response rule, you can override the API responses triggered by XHR/fetch. No need to hardcode API responses in frontend code anymore.

Test error paths in your code

Modify API responses to trigger different error paths in your codebase and test the flows without changing anything on backend. e.g. Simulate Payment Timeout Issue, Item out of stock Issue, etc.

1-Click Sharing

Use-Cases in teams are very similar so Requestly makes it easier to share the rules with each other and collaborate faster.

Trusted by developers at


Application and use cases

Here’s how you can use Requestly’s Modify Response feature in your daily workflow

Static Response

Allows you to intercept and replace the original server response with a predefined fixed JSON or string response

Dynamic response

Gives ability to modify the server response programmatically using JavaScript. Write custom JavaScript code that runs on the intercepted response and manipulate its content.

Fake status code

Enables you to change the HTTP status code of a server response. By modifying the status code, you can simulate different server responses without actually altering the content.

Intercept & Modify HTTP Requests

Boost Your Web Development: Advanced Tools for Seamless Debugging.

More from Requestly

An open-source platform that speeds up your web development cycle 10X faster.

Session Recording

Data rich bug reporting with Network logs, Console logs, Session Video and environment details. Share it with your Engineering team for faster debugging.

Mock API Server

Generate custom API responses without actually having a pre-built API or a backend server. Edit Content-Type, Status Code, Headers, and Response body easily on the Mock Server.

Web-based API Client

A comprehensive and web-based tool for modifying and testing APIs. You can test the Mock APIs you’re creating here to fast track your development lifecycle.

For the developers, by the developers ❤️

From Debug to Deploy: Developers Trust Requestly

“Requestly has changed how we work for the better. By employing it to rigorously test our staging code on external websites, we've experienced a turbo-boost in our testing speed!״
Andres Velasco
Tech Lead | Making Science
“Requestly not just made it easier for us to develop, test & debug our code on our customer sites but It also helps us do engaging product demos to our prospective clients.״
Michael Levinson
Co-Founder & CPO | Joyned
“Requestly is awesome. I used to use Charles proxy in my day to day work but it always messed with my wifi. I haven't had any issues with Requestly. Requestly's UI is amazing too and great to work in.״
Carl Hand
Senior Software Engineer | Workday
“I'm a big fan of Requestly, and use it on a daily basis as a QA Engineer. It removes the need to use Charles pretty often, which is always nice. I can just use Requestly directly in Chrome״
Mike Mitchell
QA Engineer | URBN