Firefox Remote Debugging on Android: USB and Wi-Fi Guide

Prerequisites for Firefox Remote Debugging

• Desktop Firefox - a current release on Windows, macOS, or Linux. The latest Firefox version page lists the current build number.
• adb - Android Debug Bridge from Android SDK Platform Tools, on the same computer as desktop Firefox.
• Firefox for Android - installed on the phone you want to debug.
• A USB cable or Android 11+ - USB works for any connection; cable-free debugging needs Android 11 or later on the phone.

If you also debug Chrome on the same phone, the Chrome remote debugging guide covers the chrome://inspect flow, which uses the same adb connection.

How to Enable Remote Debugging on Android

• Open Settings > About phone and tap Build number seven times until "You are now a developer!" appears. The path differs by manufacturer; the Android developer options guide lists the Pixel and Samsung locations.
• Turn on USB debugging in Developer options. On Android 9 and later it sits under Settings > System > Advanced > Developer options.
• Open Firefox for Android, go to Settings, and turn on Remote debugging via USB in the Advanced section.
• Connect the phone with a USB cable and run adb devices on the computer. If the phone shows as unauthorized, accept the USB debugging prompt on its screen and run the command again.

adb devices

How to Connect From about:debugging

On the computer, type about:debugging in the desktop Firefox address bar and open the Setup tab. The screenshot below is the Setup tab in Firefox 157.0.1, captured on a TestMu AI cloud Windows 11 machine with no phone attached, so USB reads Disabled and the sidebar shows No devices discovered.

• Click Enable USB Devices. The Setup tab notes that this downloads and adds the Android USB debugging components Firefox needs.
• Check the sidebar for your phone under USB. If it is not there, click Refresh devices.
• Click Connect next to the phone, then click the phone name to open its runtime page.
• Click Inspect next to the tab you want to debug. A DevTools toolbox for that phone tab opens on the desktop.

Ignore the Network Location field for phones. The Firefox documentation states that those network steps do not work for Android; use USB or the adb Wi-Fi connection below.

How to Debug Firefox for Android Over Wi-Fi

The Firefox documentation supports a cable-free connection through adb when the phone runs Android 11 or later. The phone and the computer must be on the same network.

• On the phone, open Developer options, turn on Wireless debugging, and note the IP address and port it shows.
• Tap Pair device with pairing code to get a six-digit code and a separate pairing port.
• Pair with adb pair, then connect with adb connect using the port from the main Wireless debugging screen.
• Run adb devices to confirm the connection, keep Remote debugging via USB turned on in Firefox for Android, and click Refresh devices in about:debugging.

adb pair <phone-ip>:<pairing-port>
# enter the six-digit pairing code when prompted
adb connect <phone-ip>:<wireless-debugging-port>
adb devices

Firefox --remote-debugging-port on Desktop

Many searches for Firefox remote debugging are about this command-line flag, which is a separate feature from about:debugging. Mozilla's Remote Agent security notes say the flag starts a server that defaults to localhost:9222 and accepts loopback connections only.

# Windows
"C:\Program Files\Mozilla Firefox\firefox.exe" --remote-debugging-port=9222

# macOS / Linux
firefox --remote-debugging-port=9222

The Remote Agent speaks WebDriver BiDi. Mozilla's remote protocol preferences page notes that Chrome DevTools Protocol support has ended, so WebDriver BiDi is the only protocol on this port. Automation clients such as Selenium use it; the WebDriver BiDi guide explains the protocol.

Troubleshooting Firefox Remote Debugging

• Phone missing from the sidebar - click Refresh devices. If it is still missing, the computer is probably not authorized yet: accept the prompt on the phone and refresh again.
• adb devices lists nothing - try another cable or port, and switch the phone's USB mode from charging only to file transfer.
• Firefox for Android 68 - desktop Firefox 69 and later cannot debug Android builds based on version 68. Use desktop Firefox ESR 68 or update the phone's Firefox.
• Wi-Fi device disappears - run adb connect again with the current port from the Wireless debugging screen, then refresh about:debugging.

Note: Need to check the same page on phones and Firefox versions you don't own? Run it on real devices and desktop browsers with TestMu AI. Start testing free

Debugging Across More Devices and Browsers

A USB phone covers one device and one Firefox build. TestMu AI Real-Time Testing opens live sessions on 3,000+ browser and OS configurations, and its session toolbar launches Firefox DevTools inside desktop Firefox, so you can test on Firefox browsers across multiple versions without installing them.

For Android-specific rendering, the TestMu AI real device cloud runs 50,000+ real Android and iOS devices with Chrome DevTools, device logs, and network logs in the session. The developer tools documentation shows how to open DevTools in a session and notes that Android DevTools need Android 7.0 or later.

Conclusion

Start with USB: turn on USB debugging and Remote debugging via USB, click Enable USB Devices in about:debugging, and inspect one tab from your staging site. When you need Firefox versions you don't have installed, open a desktop session with the Real-Time Testing getting-started guide. For iPhones, the iOS Safari remote debugging guide covers Safari Web Inspector.

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