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Troubleshoot network interference

At a glance
Goal: Fix apps losing connectivity when Dev Proxy runs
Time: 5 minutes
Plugins: None
Prerequisites: Set up Dev Proxy

Some applications lose network connectivity while Dev Proxy is running, even when their URLs aren't in your urlsToWatch list. This article explains why it happens and how to fix it.

Symptoms

  • Applications like Outlook, WhatsApp, or other desktop apps stop working when Dev Proxy starts
  • Apps show connection errors even though their URLs aren't being watched
  • Network connectivity returns immediately when you stop Dev Proxy

Cause

When Dev Proxy registers itself as a system proxy (the default behavior), all HTTP/HTTPS traffic on your machine flows through it. Some applications use certificate pinning, meaning they only accept connections signed by specific certificates. Because Dev Proxy uses its own certificate to intercept traffic, these apps reject the connection and lose network access.

This issue is most common on Windows, where applications automatically use the system proxy settings.

Solutions

Choose the solution that best fits your workflow:

Option 1: Exclude URLs in Windows proxy settings

Add exceptions for problematic domains in Windows proxy settings. Traffic to these domains bypasses Dev Proxy entirely.

  1. Open Settings > Network & Internet > Proxy

  2. Under Manual proxy setup, find Use the proxy server except for addresses that start with the following entries

  3. Add the domains that are having issues, separated by semicolons. For example:

    *.outlook.com;*.office.com;*.whatsapp.com;*.whatsapp.net

  4. Select Save

Traffic to these domains now bypasses Dev Proxy while other traffic still flows through it.

Option 2: Disable system proxy mode

If you don't need Dev Proxy to intercept traffic from all applications, disable the system proxy and configure only your target application to use the proxy.

Using command line

Start Dev Proxy without registering as the system proxy:

devproxy --as-system-proxy false

Using configuration file

Add this setting to your devproxyrc.json:

{
  "asSystemProxy": false
}

Then configure your application to use Dev Proxy by setting the https_proxy environment variable:

set https_proxy=http://127.0.0.1:8000

export https_proxy=http://127.0.0.1:8000

export https_proxy=http://127.0.0.1:8000

With this setup, only applications that respect the https_proxy environment variable send traffic through Dev Proxy. Other applications connect directly to the internet.

Option 3: Watch specific processes only

Use the watchProcessNames or watchPids settings to intercept traffic only from specific applications. This approach still registers Dev Proxy as a system proxy but limits which processes have their traffic intercepted.

{
  "watchProcessNames": ["node", "dotnet"]
}

See also

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