Debug a browser (local or remote)

WebDebugX is not limited to phones. Any Chromium-based browser started with a remote debugging port can be added as a device, whether it runs on this computer or on a machine across the room.

1. Start the browser with a debugging port

The browser must be launched with the flag; you cannot turn it on in an already-running instance.

Windows

chrome.exe --remote-debugging-port=9222 --user-data-dir="D:\chrome-debug"

macOS

"/Applications/Google Chrome.app/Contents/MacOS/Google Chrome" \
  --remote-debugging-port=9222 --user-data-dir=/tmp/chrome-debug

Linux

google-chrome --remote-debugging-port=9222 --user-data-dir=/tmp/chrome-debug

Always pass –user-data-dir

Chrome refuses to open a debugging port on a profile that is already running. Pointing at a separate directory gives you a clean, isolated profile and avoids “the port is open but nothing is there”. Edge and other Chromium browsers take the same two flags.

Confirm it worked:

curl http://localhost:9222/json/version

2. Add it in WebDebugX

1. Click Add custom device at the bottom of the device list.
2. Enter the IP and the debugging port.
   • This machine → localhost (or 127.0.0.1) and 9222.
   • Another machine → that machine’s IP address and its port.
3. Confirm. The entry appears in the device list as Localhost or as a custom device.
4. Select it and click Refresh to list its open tabs.

Pages open in Chrome DevTools.

Debugging a browser on another machine

Two things have to be true, and neither is WebDebugX’s doing:

• The port must be reachable. Chromium binds the debugging port to loopback by default, so a remote machine cannot reach it without extra work — an SSH tunnel is the usual and safest answer:

  ssh -L 9222:localhost:9222 user@that-machine

  Then add localhost:9222 locally.

• The firewall must allow it if you do expose the port directly.

A debugging port is unauthenticated

Anything that can reach it can read and control every page in that browser — cookies and sessions included. Never expose one on an untrusted network, and prefer a tunnel over binding it to a public interface.

Common problems

Symptom	Cause
Port open, no pages listed	The browser was started on an existing profile — relaunch with --user-data-dir
Connection refused	The browser is not running with the flag, or the port differs
Works locally, not remotely	The port is bound to loopback; use an SSH tunnel
“Device already exists”	That IP and port pair is already in the list