Requestly: The All-in-One API Tester, Mocking, Traffic Interception & Debugging Tool for Developers

1. Requestly Makes Live Debugging Shockingly Easy

Most debugging tools are heavy. Charles Proxy, Fiddler, and Proxyman require:

installing certificates
configuring OS-level proxy settings
dealing with complex HTTPS interception
connecting devices manually

{{ This is slow and technical }}

Requestly?

Just install the extension and start modifying live browser traffic instantly.

With one click, you can:

Add or change request headers
Modify responses
Replace API endpoints
Inject scripts
Block or redirect requests

{{ All of this happens in real time, directly in your browser}}

For developers, this means no code changes, no deployment, and no waiting.

Example: Your API returns wrong data in staging

Real API endpoint

https://api.example.com/v1/products

But staging API returns:

{"error": "Database temporarily unavailable"}

Using Requestly: Fix it in 30 seconds

Step 1: Create a “Modify Response” Rule

Choose:

Trigger URL:

https://api.example.com/v1/products

Action: Replace the API response with your own JSON

{
  "success": true,
  "products": [
    { "id": 101, "name": "Laptop", "price": 55000 },
    { "id": 102, "name": "Mouse", "price": 1200 }
  ]
}

2. API Mocking Becomes Instant (Without Backend Dependence)

Every developer has faced this situation:

“The backend API isn’t ready yet — so frontend development is blocked.”

Requestly solves this completely.

Requestly lets you mock any API response instantly:

Return custom JSON
Simulate errors (400, 401, 500)
Test edge cases
Create multiple mocks for different scenarios

This lets frontend developers work independently, without waiting for backend delivery.

Backend late?
Server down?
API unstable?

No problem — Requestly keeps your development moving.

Example: Backend Not Ready? Keep Building Anywar

Your frontend needs this real API

GET https://api.example.com/v1/user/123

With Requestly: Mock It in Less Than 30 Seconds

Create a “Mock API” Rule

Trigger URL:

https://api.example.com/v1/user/123

Choose action: Mock Response

Add your mock JSON:

{
  "id": 123,
  "name": "Hasan Monsur",
  "role": "Admin",
  "status": "Active"
}

3. Perfect for Testing UI When Backend Is Unreliable

Even when backend exists, it’s often:

Unpredictable
Updating constantly
Returning unexpected results
Running on slow staging servers

Requestly allows controlled testing.

You can simulate:

Slow network
Cached responses
Failed logins
Empty lists
Corrupted data
Timeout scenarios

This helps developers uncover hidden UI issues before users ever see them.

Example: Your UI Breaks Because Staging Is Slow

GET https://api.example.com/v1/orders

With Requestly: Simulate the Problem on Purpose

Example Rule: Add Delay to API Response

Trigger URL:

https://api.example.com/v1/orders

Action: Add Network Delay: 8000 ms (8 seconds)

4. Rewrite, Redirect, Inject, and Override Anything in the Browser

One of the biggest reasons developers love Requestly is its flexibility.

You can modify almost every aspect of a web request or response.

Examples:

✔ Redirect API calls from production → local environment
✔ Replace a JavaScript file without deploying
✔ Override feature-flag responses
✔ Inject custom CSS or JS into live pages
✔ Test frontend changes in production safely
✔ Switch environments without editing env files

This is incredibly powerful for rapid experimentation.

Example: Redirect Production API → Localhost Without Changing Code

Let’s say your frontend calls the production API:

https://api.example.com/v1/auth/login

But you want to test your new .NET backend running on:

http://localhost:5000/v1/auth/login

With Requestly: Do It in 10 Seconds

Create a Redirect Rule:

Match URL:

https://api.example.com/v1/auth/login

Redirect To:

http://localhost:5000/v1/auth/login

Your production frontend now talks to your local backend — without editing a single line of code.

5. A Must-Have Tool for QA, Testers, and Automation Engineers

Requestly isn’t just for developers — QA teams use it heavily.

QA can use it to:

Inject test data
Simulate error states
Mock edge-case responses
Validate UI behavior
Test without touching backend servers
Reproduce production bugs quickly

This dramatically reduces test time and improves accuracy.

For automation engineers, Requestly works perfectly alongside tools like Cypress, Selenium, or Playwright to simulate different server responses.

Example: QA Needs to Test “Expired Session” Error

{ "status": "active" }

Backend replies: “We can’t reproduce it right now.” Testing is blocked.

With Requestly: Create the Error Instantly

Create a Mock Response Rule:

Match URL:

https://api.example.com/v1/session/check

Mock JSON:

{
  "status": "expired",
  "message": "Your session has expired. Please log in again."
}

QA can now test the expired-session UI flow immediately — no backend support required.

6. Requestly Replaces 4–5 Tools with One

Most teams use multiple tools to solve different debugging problems:

ModHeader → for headers
Charles Proxy → for traffic interception
Local mock server → for mocking
Script injections → added manually
Query parameter overrides → managed in config

Requestly does ALL of this from one unified interface.

That means:

less setup
less confusion
faster debugging
fewer tools to maintain

This is why teams love it — it simplifies everything.

Example: A Developer Trying to Fix One Simple Bug

Problem:

You need to debug a checkout API issue and test a new JS file.

Normally, you’d need four tools:

ModHeader → Add auth headers
Charles Proxy → Intercept/modify the API
Local mock server → Generate mock data
Manual script injection → Load new JS file

With Requestly: Do It All in One Place

Within Requestly:

Modify header: Add temporary JWT
Mock API: Replace checkout response with your custom JSON
Redirect JS file:
Redirect production file:

https://cdn.example.com/checkout.js

To your local version:

http://localhost:3000/checkout.js

Simulate delay: Add 3-second delay to test loading states
Inject script: Add debugging console logs

All handled inside one rule set — with zero external tools.

You test everything quickly, cleanly, and consistently.

7. Shared Rules Make Team Collaboration Much Easier

Debugging is easier when everyone is on the same page.

Requestly allows you to share rules, mock APIs, environments, and configurations across your whole team.

For example:

Share mock server for a new feature
Share environment redirects
Share bug reproduction setups
Share response overrides

This is extremely useful for:

Dev teams
QA teams
Automation teams
Cross-functional squads

Everyone stays aligned without confusion.

Example: QA Finds a Critical Bug — Dev Team Reproduces It in One Click

QA reports a bug happening only when the API returns odd data:

{
  "orders": "unknown_format"
}

With Requestly: QA Shares the Rule Instantly

QA creates a Mock Response Rule and clicks “Share Rule.”

Developers receive a link, open it, and activate the rule.

Result:

QA and Dev see the same API response
Developers reproduce the bug instantly
No environment setup needed
No back-and-forth guessing

8. Debug Production Safely Without Code Changes

Sometimes, bugs only appear in production — and developers cannot modify the code or server instantly.

Requestly solves this by letting you modify the browser behavior locally, WITHOUT changing anything in production.

You can:

Inject logging
Override API failures
Replay user scenarios
Fix temporary UI behavior for testing
Replace broken endpoints locally

This is a lifesaver for fast debugging.

Example: A Production API Starts Returning Unexpected Errors

Your production endpoint:

https://app.example.com/api/cart

suddenly returns:

500 Internal Server Error

With Requestly: Debug Production Without Touching Production

Create a Mock Response Rule:

Match:

https://app.example.com/api/cart

Override with JSON:

{ "items": [], "status": "temporary-fix" }

Now you can observe how UI behaves as if the bug is fixed, without touching production servers.

Or simulate the crash:

{ "error": "Simulated server failure" }

9. Faster Development = Lower Costs & Higher Productivity

Requestly removes countless pain points:

❌ Waiting for backend
❌ Editing environment files
❌ Restarting apps
❌ Rebuilding projects
❌ Temporary hack code
❌ Delayed integration

✔ Faster UI development
✔ Faster API integration
✔ Rapid debugging
✔ Easy mocking
✔ Less developer frustration

For companies, this means:

faster release cycles
better team productivity
fewer bugs reaching users

Example: A Simple UI Change That Normally Wastes Hours

You’re building a new dashboard UI, but the backend API is still unstable.

Normally you would:

Wait for backend to finalize
Edit environment variables
Restart the app
Rebuild after every config change
Comment/uncomment temporary hack code
Pray staging doesn’t break again

With Requestly: Build UI in Full Speed

Using a Mock Response Rule:

Match:

https://api.example.com/v1/dashboard

Mock:

{
  "name": "Test User",
  "stats": { "orders": 42, "notifications": 8 }
}

Conclusion:

Requestly is not just another debugging tool — it’s a productivity booster that removes blockers across the entire development lifecycle.

Whether you’re a frontend engineer, backend developer, QA tester, automation engineer, or tech lead, Requestly helps you:

debug faster
test better
ship quicker
collaborate smoother

No heavy setup. No backend dependency. No complicated proxies.

Just instant, powerful debugging — right inside your browser.

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