DEV Community: HttpTracer

How to Use the RESTful API Features in HttpTracer

HttpTracer — Tue, 23 Dec 2025 18:30:00 +0000

HttpTracer includes a powerful RESTful API Composer that lets you craft and send custom HTTP requests directly from the app. Whether you're testing an API, replaying a captured request, or debugging a specific endpoint, the RESTful features give you full control over your HTTP traffic.

In this post, we'll explore two key ways to use this feature:

The RESTful Page – For building requests from scratch
The RESTful API Tab in the Inspector Panel – For replaying and modifying captured requests

1. The RESTful Page: Craft Requests From Scratch

Navigate to the RESTful page from the left sidebar. This is your workspace for building custom HTTP requests.

Setting Up Your Request

URL and Method

At the top, you'll find the URL input field and a dropdown to select the HTTP method (GET, POST, PUT, PATCH, DELETE, etc.). Simply enter the endpoint you want to call.

Request Headers

Switch to the Headers tab to add custom headers. Each header has:

A checkbox to enable/disable it
Key and Value fields

This is useful for adding authentication tokens, content types, or any custom headers your API requires.

Query Parameters

The Params tab lets you add query string parameters. HttpTracer automatically appends these to your URL, so you don't need to manually construct query strings.

Cookies

Need to send cookies? The Cookies tab provides a simple interface to add cookie key-value pairs.

Request Body Options

For POST, PUT, and PATCH requests, you can add a request body. HttpTracer supports multiple body types:

Body Type	Use Case
None	No body (typical for GET requests)
Form Data	Multipart form data with file upload support
URL Encoded	Standard form encoding (`application/x-www-form-urlencoded`)
Raw	JSON, XML, HTML, JavaScript, or plain text
Binary	Upload binary files

Raw Body Editor

When using the Raw body type, you get a full-featured code editor with syntax highlighting. Select the content type (JSON, XML, HTML, etc.) and HttpTracer will set the appropriate Content-Type header.

Form Data with File Uploads

The Form Data option lets you add text fields or file uploads. This is perfect for testing file upload endpoints.

Sending the Request

Click the Send button to execute your request. The response appears in the right panel, showing:

Status Code and status message
Response Headers
Response Body (formatted based on content type)

2. The RESTful API Tab in the Inspector Panel

One of the most useful features is the ability to replay captured requests directly. When you're inspecting network traffic, you can open any captured request in the RESTful composer.

How to Access It

Capture traffic as usual (enable the proxy and make requests)
Select a request from the traffic list
In the right panel, click the RESTful API tab

What Gets Loaded

When you open a captured request in the RESTful tab, HttpTracer automatically populates:

The original URL and HTTP method
All headers from the captured request
Query parameters (parsed from the URL)
The request body (if present)

[!TIP]
You can modify any of these values before resending. This is great for testing variations of an API call without manually reconstructing the entire request.

Opening in Full Composer

If you need more space to work, click the expand icon next to the "RESTful API" tab label. This opens the request in the full RESTful page with all its features.

Practical Use Cases

1. Testing API Changes

Made a change to your backend? Replay a captured request to verify the change works as expected.

2. Debugging Authentication Issues

Captured a failing request? Modify the auth headers and resend to pinpoint the issue.

3. Exploring Third-Party APIs

Capture a request from your app to a third-party API, then modify it to explore different parameters or endpoints.

4. Reproducing Bugs

Found a bug? Capture the problematic request and replay it with variations to understand the exact conditions that trigger the issue.

Tips for Power Users

Disable headers temporarily – Use the checkboxes to toggle headers on/off without deleting them
Check the response timing – The Overview tab shows detailed timing information
Look out for pseudo-headers – HTTP/2 pseudo-headers (like :method, :path) are automatically disabled when replaying, as they're protocol-specific

Summary

The RESTful features in HttpTracer give you powerful tools for API development and debugging:

Feature	Location	Best For
RESTful Page	Left sidebar	Building new requests from scratch
RESTful API Tab	Inspector panel	Replaying and modifying captured requests

Combined with HttpTracer's traffic inspection capabilities, you have a complete toolkit for understanding and testing HTTP traffic.

Download HttpTracer now!
Have questions or feedback? Let us know!

How to Use the Rules Feature in HttpTracer

HttpTracer — Sat, 20 Dec 2025 07:16:37 +0000

The Rules feature in HttpTracer is one of the most powerful tools for developers who want to intercept and modify network traffic on the fly. Whether you're debugging API responses, testing error handling, or simulating different server behaviors, Rules gives you full control over HTTP requests and responses.

In this guide, we'll walk you through everything you need to know to get started with Rules.

What Are Rules?

Rules allow you to:

Match specific network requests based on URL, method, headers, query parameters, and more
Modify requests before they're sent to the server (change headers, query params, redirect to a different URL)
Modify responses before they reach your app (change status codes, headers, or even replace the entire response body)

This is incredibly useful for:

🐛 Debugging: Test how your app handles different API responses without changing server code
🧪 Testing edge cases: Simulate 500 errors, slow responses, or unexpected data
🔄 Mocking APIs: Return custom responses for endpoints that don't exist yet

Getting Started with Rules

Step 1: Open the Rules Editor

Click on the Rules tab in the sidebar to open the Rules Editor.

You'll see a three-panel interface:

Left Panel: Rule Groups and Rules tree
Center/Right Panel: Rule configuration (Matchers and Actions)

Step 2: Create a Rule Group

Rules are organized into Groups for better organization. Think of groups as folders for your rules.

Click the "+ Group" button in the left panel
A new group called "New Group" will appear
Double-click the group name to rename it (e.g., "API Debugging Rules")

Step 3: Add a Rule

With your group selected:

Click the "+ Rule" button or right-click the group and select "Add Rule"
A new rule called "New Rule" will be created
Click on the rule to select it and start configuring

Configuring Your Rule

Every rule has two main parts:

Matchers - Define WHICH requests/responses this rule applies to
Actions - Define WHAT to do with matched traffic

Matchers: Targeting Specific Traffic

The Matchers section lets you specify which network requests should be affected by this rule.

Available Request Matchers:

Matcher	Description	Example
Method	HTTP method (GET, POST, etc.)	Match only POST requests
Protocol	HTTP or HTTPS	Match only HTTPS requests
URL	Full URL matching	Match `api.example.com/users`
Hostname	Just the domain	Match `api.example.com`
Path	URL path only	Match `/api/v1/users`
Headers	Request headers	Match requests with `Authorization` header
Query Params	URL query parameters	Match requests with `?debug=true`

Matching Conditions:

Each matcher supports different conditions:

equals - Exact match
contains - Partial match
starts-with - Match beginning
ends-with - Match ending
regex - Regular expression pattern
not-equals - Inverse match

Example: To match all GET requests to api.example.com:

Set Method to GET
Set Hostname condition to equals with value api.example.com

Actions: Modifying Traffic

Once you've defined what traffic to match, you can specify what to do with it.

Modify Request Actions:

Enable "Modify Request" to change the request before it's sent:

Change Method: Switch GET to POST, etc.
Change URL/Hostname/Path: Redirect requests to different servers
Add/Remove/Edit Headers: Add authentication, modify content types
Add/Remove/Edit Query Params: Inject or remove URL parameters

Modify Response Actions:

Enable "Modify Response" to change the response before your app receives it:

Change Status Code: Return 200, 404, 500, etc.
Add/Remove/Edit Headers: Modify CORS headers, caching, etc.
Override Body: Return custom JSON, HTML, or load from a file

Practical Examples

Example 1: Simulate an API Error

Goal: Test how your app handles a 500 server error from /api/users

Create a new rule
Matchers:
- Path: contains → /api/users
Actions:
- Enable "Modify Response"
- Set Status Code to 500
- Optionally set body to {"error": "Internal Server Error"}

Now any request to /api/users will return a 500 error!

Example 2: Add Debug Headers

Goal: Add a custom header to all API requests

Create a new rule
Matchers:
- Hostname: contains → api.
Actions:
- Enable "Modify Request"
- Add Header: X-Debug-Mode = true

All requests to domains containing "api." will now include your debug header.

Example 3: Mock an API Response

Goal: Return fake data for an endpoint that doesn't exist yet

Create a new rule
Matchers:
- Path: equals → /api/v2/new-feature
Actions:
- Enable "Modify Response"
- Set Status Code to 200
- Set Body to:

{
  "feature": "enabled",
  "data": ["item1", "item2", "item3"]
}

Tips & Best Practices

1. Use Rule Groups Effectively

Organize your rules by project, feature, or purpose. You can enable/disable entire groups at once.

2. Toggle Rules On/Off

Each rule has an active toggle. Disable rules you're not currently using without deleting them.

3. Use Regex for Complex Matching

Need to match /users/123 and /users/456? Use regex: /users/\d+

4. Test with Live Traffic

Open the Live panel alongside Rules to see your modifications in real-time.

5. Duplicate Rules

Right-click a rule to duplicate it – great for creating variations of existing rules.

Troubleshooting

Rule Not Working?

Check if the rule is active - Look for the toggle switch
Check if the group is active - Groups can also be disabled
Verify your matchers - Make sure the conditions actually match your traffic
Check the order - Rules are processed in order; earlier rules take precedence

Need More Power?

Consider upgrading your plan to create more rule groups and rules per group.

Summary

The Rules feature transforms HttpTracer from a simple traffic viewer into a powerful debugging and testing tool. By setting up the right matchers and actions, you can:

✅ Test error handling without changing server code
✅ Mock APIs during development
✅ Debug complex request/response flows
✅ Simulate edge cases and rare scenarios

Start with simple rules and gradually explore more advanced features like regex matching, header manipulation, and response body overrides.

Happy debugging with HttpTracer 🚀