Device not found

Two different failures look similar. Work out which one you have first — it halves the search space.

• The device is not in the list at all → a connection or authorization problem.
• The device is listed but shows no pages → an inspector-switch or page-state problem.

The device is not listed

1. The cable and the port

The most common cause, and the least suspected. Many cables are charge-only.

• Swap the cable for one you know carries data.
• Try a different USB port — prefer one directly on the machine over a hub.
• On a desktop, prefer a rear port.

2. Unlocked and trusted

• iOS — unlock the device. Tap Trust on the Trust this computer? prompt and enter the passcode. If you previously tapped Don’t Trust, unplug, relock, reconnect. To clear a bad state: Settings → General → Transfer or Reset iPhone → Reset → Reset Location & Privacy, then reconnect and accept.
• Android — pull down the USB notification and select File transfer. Accept Allow USB debugging?. If that prompt never appears, go to Developer options → Revoke USB debugging authorizations and reconnect.

3. The platform driver (Windows)

Windows cannot see an iPhone without Apple’s USB driver. Install Apple Devices from the Microsoft Store (or iTunes) and reconnect. Some Android vendors also ship their own driver.

4. Refresh

Click Refresh in the device list. Toggles you flip on the device are not retroactively applied to an already-enumerated device.

5. Confirm it is not WebDebugX

Check whether the platform tooling sees the device at all:

adb devices     # Android — should list the serial as "device", not "unauthorized"

• unauthorized → the trust prompt has not been accepted.
• Empty list → the problem is the cable, the port, the driver or the mode, and no debugging tool will see it.

6. Restart, in this order

Cheapest first: reconnect the cable → restart WebDebugX → restart the device → restart the computer.

The device is listed but no pages appear

1. Is the inspector switch on?

• iOS Safari — Settings → Safari → Advanced → Web Inspector.
• iOS Chrome — Chrome → ⋯ → Settings → Content Settings → Web Inspector. Separate from Safari’s.
• Android browser tabs — USB debugging is enough; no separate switch.
• In-app pages — the app must enable it in code. See Debug in-app pages.

2. Is the page actually open?

An inspectable page has to exist. Bring the tab to the front, or navigate the app to the screen that hosts the web view. A tab the OS discarded to save memory exposes nothing until it is reloaded.

3. Refresh, then reload

Click Refresh in WebDebugX. If the switch was flipped while the page was already open, reload the page on the device too.

4. Right app, right build?

An older build without the debugging flag is indistinguishable from the outside. Reinstall the build that has it.

The page opens but the session drops

• Screen lock. Locking the device can end the session. Keep the screen on; extend auto-lock while you work.
• The cable moved. A marginal cable disconnects under its own weight.
• The page navigated away. A full navigation replaces the target; refresh the list and reattach.

Custom device (browser) issues

See Debug a browser — the usual cause is a browser started on an existing profile without --user-data-dir, which silently refuses to open the port.