[TOOL] INTERCEPT & MODIFY HTTP/HTTPS REQUESTS FROM APPS IN REAL TIME [2026]

Kinder · Oct 12, 2026

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Ever wondered exactly what information an application sends to a server — and what happens if you change that information before it arrives?

There's an open-source tool called mitmproxy that lets you intercept, inspect, modify, and replay HTTP/HTTPS requests.

Think of it as a powerful traffic inspection and debugging environment.

You can see the communication between a client and a server, inspect JSON payloads, change requests, and analyse the responses.

It's completely free, scriptable, and supports Windows, Linux, and macOS.

WHAT MAKES IT INTERESTING?mitmproxy can:
- Capture HTTP and HTTPS traffic

- Inspect API requests and responses

- View JSON data and HTTP headers

- Pause requests before they're sent

- Edit request parameters

- Modify server responses

- Replay previous requests

- Filter traffic by domain or URL

- Save complete HTTP conversations

- Automate traffic transformations using Python

It's useful for debugging your own applications, examining web protocols, testing API validation, and researching security issues in authorised environments.

OFFICIAL LINKSWebsite:

https://mitmproxy.org/

Download:

https://mitmproxy.org/

GitHub:

https://github.com/mitmproxy/mitmproxy

Official Releases:

https://github.com/mitmproxy/mitmproxy/releases

Documentation:

https://docs.mitmproxy.org/stable/

Interception Tutorial:

https://docs.mitmproxy.org/stable/mitmpr...trequests/

STEP 1 — INSTALL MITMPROXYDownload the Windows installer from:

https://mitmproxy.org/

Complete the installation.

The installer provides three main tools:

Code:

Code:

mitmproxy Interactive terminal interface mitmweb Browser-based graphical interface mitmdump Command-line traffic capture

We'll use mitmweb because its interface makes inspecting and changing requests easier.

STEP 2 — START THE WEB INTERFACEOpen PowerShell.

Run:

Code:

Code:

mitmweb

The tool starts a local proxy, normally listening on:

Code:

Code:

127.0.0.1:8080

It also launches its web interface in your browser.

Leave the PowerShell window open.

STEP 3 — ROUTE TEST TRAFFIC THROUGH THE PROXYYou don't need to configure your entire computer.

For the first demonstration, use PowerShell with curl.

Open a second terminal.

Run:

Code:

Code:

curl.exe --proxy http://127.0.0.1:8080 http://example.com/

Return to mitmweb.

You should see an HTTP request appear in the traffic list.

Select it to inspect the request and response.

This demonstrates the basic interception process without changing global network settings.

STEP 4 — UNDERSTAND THE REQUESTAn HTTP request contains information such as:

Code:

Code:

GET / HTTP/1.1 Host: example.com User-Agent: curl Accept: */*

The server then returns an HTTP response.

For example:

Code:

Code:

HTTP/1.1 200 OK Content-Type: text/html

The exact response depends on the server.

mitmproxy presents these exchanges as individual flows.

Each flow lets you inspect the request and its corresponding response.

STEP 5 — BUILD A LOCAL TEST APINow for a more interesting demonstration.

We'll create a tiny API that accepts JSON requests.

This keeps the entire experiment on your own computer.

Create a file called:

Code:

Code:

server.py

Paste:

Code:

Code:

from http.server import BaseHTTPRequestHandler, HTTPServer import json class Handler(BaseHTTPRequestHandler): def do_POST(self): length = int(self.headers.get("Content-Length", "0")) body = self.rfile.read(length) try: data = json.loads(body) except (ValueError, UnicodeDecodeError): data = {} response = { "received": data, "message": "Local test API" } output = json.dumps(response).encode() self.send_response(200) self.send_header("Content-Type", "application/json") self.send_header("Content-Length", str(len(output))) self.end_headers() self.wfile.write(output) HTTPServer(("127.0.0.1", 9000), Handler).serve_forever()

Run:

Code:

Code:

python server.py

Your local API is now listening on:

Code:

Code:

http://127.0.0.1:9000

STEP 6 — SEND A REQUEST THROUGH MITMPROXYOpen a third PowerShell window.

Execute:

Code:

Code:

curl.exe --noproxy "" --proxy http://127.0.0.1:8080 ` -X POST http://127.0.0.1:9000/test ` -H "Content-Type: application/json" ` -d '{"username":"testuser","level":1}'

On Windows,

Code:

Code:

curl.exe

is used explicitly to avoid PowerShell aliases.The

Code:

Code:

--noproxy ""

option prevents an existing localhost proxy bypass from overriding the supplied proxy.Return to mitmweb.

You should see the POST request.

Select it to inspect the JSON body.

STEP 7 — INTERCEPT AND MODIFY A REQUESTThis is where the tool becomes particularly useful.

In mitmweb, enable request interception and configure it to target your local test endpoint.

Send the POST request again.

When the request is paused, inspect its body.

Original:

Code:

Code:

{ "username": "testuser", "level": 1 }

Edit the JSON to:

Code:

Code:

{ "username": "testuser", "level": 99 }

Resume the request.

Your test server should return the modified JSON because it echoes the request body.

You've now demonstrated live HTTP request manipulation using your own API.

Note that changing a client-supplied value doesn't automatically change trusted server-side account permissions. A secure real application must validate such values independently.

STEP 8 — REPLAY A REQUESTmitmproxy can replay saved HTTP conversations.

Select a previously recorded request.

Use the interface's replay functionality to send it again.

This is useful for reproducing bugs and comparing API responses after changing your application's code.

For example, you can test whether your local API consistently accepts the same JSON payload.

Replaying a request is not guaranteed to reproduce the same outcome if the server maintains state.

BONUS — CAPTURE HTTPS TRAFFICFor your own test applications, mitmproxy also supports HTTPS inspection.

To decrypt HTTPS traffic, the client must trust mitmproxy's local certificate authority.

With the proxy configured, open:

http://mitm.it/

Follow the official certificate setup instructions for your test environment.

Once properly configured, you can inspect supported HTTPS requests and responses.

Important: Installing a trusted local CA gives the proxy significant visibility into HTTPS traffic from clients that trust it.

Use it only in environments you control, and remove the test CA when finished.

Some applications use certificate pinning or custom networking stacks and won't be inspectable through ordinary proxy configuration.

BONUS #2 — CAPTURE ONE APPLICATIONmitmproxy supports local capture modes on supported operating systems.

For example:

Code:

Code:

mitmproxy --mode local:curl

This targets traffic generated by processes matching

Code:

Code:

curl

.The feature is useful when testing a particular application without capturing unrelated network traffic.

See:

https://docs.mitmproxy.org/stable/concepts/modes/

BONUS #3 — AUTOMATE REQUEST MODIFICATIONSmitmproxy supports Python addons.

For example, create:

Code:

Code:

modify.py

Add:

Code:

Code:

from mitmproxy import http def request(flow: http.HTTPFlow): if ( flow.request.pretty_host == "127.0.0.1" and flow.request.path == "/test" ): flow.request.headers["X-Lab-Test"] = "enabled"

Start mitmweb with:

Code:

Code:

mitmweb -s modify.py

Requests to your local

Code:

Code:

/test

endpoint will receive the additional header.This demonstrates how to automate controlled request transformations.

More advanced addons can work with request bodies, responses, and different traffic filters.

BONUS #4 — SAVE TRAFFIC FOR ANALYSISmitmproxy supports saving HTTP flows to a file for later analysis.

For example:

Code:

Code:

mitmdump -w capture.mitm

This starts the command-line proxy and records traffic routed through it.

You can later inspect compatible saved flows using mitmproxy's tools.

Saved traffic may contain authentication tokens, personal information and other secrets.

Protect your captures and avoid publishing them without appropriate sanitisation.

BONUS #5 — WHAT ELSE CAN YOU TEST?In applications you own or are authorised to assess, mitmproxy can help investigate:

API Validation

Does your server reject malformed or unexpected JSON?

Error Handling

Does your application display useful errors when a server returns an unexpected response?

Session Management

Does your backend correctly validate authentication independently of client-controlled input?

Privacy

Which network requests does your own application make?

Performance

How does your application behave when requests are delayed or responses are modified?

IMPORTANT LIMITATIONSmitmproxy is not a universal traffic decryption tool.

It cannot automatically inspect every application or protocol.

Limitations include:
- Client proxy configuration

- Certificate trust requirements

- Certificate pinning

- Unsupported protocols

- Encrypted payloads within HTTPS

- Application-specific networking

- Traffic that never reaches the configured proxy

Use the appropriate capture mode for your environment.

IS IT STILL MAINTAINED IN 2026?Yes.

The project's official changelog documents mitmproxy 12.2.3, released on 12 May 2026.

It includes fixes involving certificate handling, the web interface and traffic export.

The official project repository also maintains newer development changes.

SOURCEShttps://mitmproxy.org/

https://github.com/mitmproxy/mitmproxy

https://docs.mitmproxy.org/stable/overvi...tallation/

https://docs.mitmproxy.org/stable/overvi...g-started/

https://docs.mitmproxy.org/stable/mitmpr...trequests/

https://docs.mitmproxy.org/stable/mitmpr...yrequests/

mitmproxy is a powerful open-source tool for understanding and controlling HTTP communication in authorised testing environments.

It's useful for web development, API security research, debugging and protocol analysis — without paying for a commercial interception suite.

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Master15pk · Oct 20, 2026

Thank good

[TOOL] INTERCEPT & MODIFY HTTP/HTTPS REQUESTS FROM APPS IN REAL TIME [2026]

Kinder

Master15pk

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