How to Configure Proxy Settings in Postman for API Testing

Postman is the most popular API testing and development tool, used by millions of developers to send requests, test endpoints, and debug APIs. Configuring a proxy in Postman allows you to route API requests through a specific IP address, capture traffic for inspection, or test how APIs respond from different geographic locations.

This guide covers how to configure both outgoing proxies (for routing your requests) and Postman’s built-in proxy server (for capturing traffic from other devices), along with SSL certificate handling and authentication.

Why Use a Proxy with Postman

There are several practical reasons to configure proxy settings in Postman:

API testing from different regions — Test geo-restricted APIs by routing requests through proxies in specific countries
Network debugging — Route Postman traffic through a debugging proxy like Charles or Fiddler to inspect requests and responses
IP rotation — Avoid rate limiting when testing APIs extensively
Corporate network access — Many corporate networks require a proxy for outbound internet access
Security testing — Intercept and modify API requests for penetration testing
Privacy — Hide your development machine’s IP from external APIs

Method 1: Configure an Outgoing Proxy in Postman

This routes Postman’s API requests through your proxy server.

Step 1: Open Proxy Settings

Open Postman.
Click the gear icon (Settings) in the top-right corner, or go to File > Settings (Windows/Linux) or Postman > Settings (macOS).
Click the Proxy tab.

Step 2: Configure the Proxy

Under Proxy configurations for sending requests, toggle Use the system proxy off (if you want to use a custom proxy instead of the system proxy).
Toggle Use custom proxy configuration to On.
Select the proxy type:

HTTP — For standard HTTP proxies
HTTPS — For encrypted proxy connections

Enter the proxy details:

Proxy Server: proxy.example.com
Port: 8080

If the proxy requires authentication:

Toggle Proxy Auth to On
Enter your Username and Password

Step 3: Configure Proxy Bypass

In the No Proxy field, enter hosts that should bypass the proxy:

localhost, 127.0.0.1, *.local, 192.168.*

Separate entries with commas.

Step 4: Test the Configuration

Create a new request in Postman.
Set the URL to https://api.ipify.org?format=json.
Click Send.
The response should show the proxy server’s IP address, confirming the proxy is active.

Method 2: Use the System Proxy

Postman can use your operating system’s proxy settings:

Go to Settings > Proxy.
Toggle Use the system proxy to On.
Postman will automatically use whatever proxy is configured at the OS level.

This is the simplest approach if you already have a system proxy configured.

Method 3: Set Up Postman’s Built-In Proxy Server

Postman has a built-in proxy that can capture HTTP/HTTPS traffic from other devices and applications. This is useful for capturing mobile app API calls.

Step 1: Enable the Proxy Server

In Postman, click the Capture icon in the bottom toolbar (or go to the footer bar and click “Capture requests”).
Select Via Proxy.
Configure:

Port: Default is 5555 (you can change this)
Target: Choose to save captured requests to a collection or the History

Step 2: Configure Your Device to Use Postman’s Proxy

On the device whose traffic you want to capture:

Set the proxy to your computer’s local IP address.
Set the port to 5555 (or whatever you configured).
For example, on an iPhone: Settings > Wi-Fi > (your network) > Configure Proxy > Manual > Server: 192.168.1.100, Port: 5555.

Step 3: Capture HTTPS Traffic

To capture HTTPS traffic, you need to install Postman’s SSL certificate on the device:

In the Capture window, click Download Certificate.
Transfer the certificate to your device.
Install and trust the certificate.
HTTPS requests will now be captured and decrypted.

Step 4: View Captured Requests

Captured requests appear in your specified collection or History. You can inspect headers, bodies, and response data.

Configuring Proxy for Specific Request Types

Environment-Based Proxy Configuration

Use Postman environments to manage proxy settings for different projects:

Create a new Environment (e.g., “Production via Proxy”).
Add variables:

proxy_host: proxy.example.com
proxy_port: 8080
proxy_user: username
proxy_pass: password

While Postman’s built-in proxy settings do not directly support environment variables, you can use these variables in pre-request scripts.

Pre-Request Script Proxy Handling

Use pre-request scripts to add proxy-related headers or modify requests:

// Add custom headers that your proxy might require
pm.request.headers.add({
    key: "Proxy-Authorization",
    value: "Basic " + btoa(pm.environment.get("proxy_user") + ":" + pm.environment.get("proxy_pass"))
});

Collection-Level Proxy Settings

When sharing collections with teams, document proxy requirements:

Open the collection.
Click Edit and go to the Documentation tab.
Document the proxy configuration needed for the collection.

Using Postman with Debugging Proxies

Charles Proxy Integration

Start Charles Proxy on your computer (default port: 8888).
In Postman, set the custom proxy to 127.0.0.1:8888.
Install Charles’ SSL certificate if you need to inspect HTTPS traffic.
Send requests from Postman — they appear in Charles for inspection.

Fiddler Integration

Start Fiddler (default port: 8866).
In Postman, set the custom proxy to 127.0.0.1:8866.
Configure Fiddler’s HTTPS decryption if needed.
Monitor Postman traffic in Fiddler.

mitmproxy Integration

Start mitmproxy: mitmproxy --listen-port 8080
In Postman, set the custom proxy to 127.0.0.1:8080.
Install the mitmproxy certificate in your system’s trusted certificates.
Inspect traffic in the mitmproxy console.

Handling SSL Certificates with Proxies

When routing HTTPS traffic through a proxy, certificate issues are common.

Disable SSL Verification (Development Only)

Go to Settings > General.
Toggle SSL certificate verification to Off.

Warning: Only disable SSL verification in development environments. Never disable it when testing production APIs or handling sensitive data.

Add Custom CA Certificates

For corporate proxies that perform SSL interception:

Go to Settings > Certificates.
Toggle CA Certificates to On.
Click Select File and choose your corporate CA certificate (PEM format).
Postman will trust certificates signed by this CA.

Client Certificates

If your proxy requires client certificate authentication:

Go to Settings > Certificates.
Under Client Certificates, click Add Certificate.
Enter:

Host: The domain or IP
CRT file: Your client certificate
KEY file: Your private key
Passphrase: If the key is encrypted

Click Add.

API Testing Scenarios with Proxies

Testing Geo-Restricted APIs

Some APIs return different data based on the requester’s location:

Configure a proxy in the target country using a mobile proxy.
Send the same API request through different regional proxies.
Compare responses to verify geo-dependent behavior.

Load Testing with IP Rotation

When load testing APIs, rotating proxies prevent your IP from being rate-limited:

Configure multiple proxy profiles in Postman environments.
Switch between environments to use different proxies.
For automated load testing, use Postman’s Collection Runner with different proxy configurations.

Monitoring API Changes

Set up recurring API tests through a proxy to monitor external APIs for data collection:

Create a Postman Monitor.
Configure the proxy settings.
Schedule the monitor to run at intervals.
Review results for unexpected changes.

Troubleshooting Postman Proxy Issues

“Could not get any response” Error

Verify the proxy address and port are correct.
Test the proxy with curl: curl -x http://proxy:8080 https://api.ipify.org
Check that the proxy server is running and accessible.
Ensure your firewall allows Postman to make outbound connections.

SSL Certificate Errors

If using a debugging proxy, install its CA certificate (see SSL section above).
For testing, temporarily disable SSL verification in Postman settings.
Ensure your proxy supports HTTPS CONNECT tunneling.

Authentication Failures

Verify username and password.
Check if the proxy uses Basic or NTLM authentication — Postman supports Basic.
Try the proxy without authentication to isolate the issue.
Some proxies use IP-based authentication — ensure your IP is whitelisted.

Proxy Works in Browser but Not Postman

Postman uses its own network stack, not the browser’s.
Ensure the custom proxy is configured in Postman’s settings, not just the system proxy.
Check if the proxy requires specific headers that the browser adds automatically.

Slow API Responses Through Proxy

The proxy adds network latency to every request.
For performance testing, note the proxy overhead and account for it in results.
Use a proxy geographically close to either you or the API server.

For a reference on proxy terminology used in this guide, visit our proxy glossary.

Best Practices

Use environment variables to manage proxy configurations across different testing scenarios.
Document proxy requirements in your collection description for team collaboration.
Keep SSL verification on in production testing — only disable for local debugging.
Use Postman’s built-in proxy for capturing mobile app traffic instead of complex network configurations.
Test without a proxy first to establish baseline response times and behavior before adding proxy-routed tests.

Conclusion

Postman provides flexible proxy support for both routing outbound requests and capturing incoming traffic. The custom proxy configuration is ideal for API testing from different regions, corporate network access, and debugging. Postman’s built-in proxy server adds powerful traffic capture capabilities for mobile app development. Whether you are testing geo-dependent APIs, debugging through Charles Proxy, or working behind a corporate firewall, Postman’s proxy features adapt to your workflow.