Stop IP leaks in Firefox via about:config
Firefox has a genuine advantage here: you can disable WebRTC completely with a single built-in setting, no extension required. Here’s the exact change through about:config.
The one-setting fix
Type about:config into the Firefox address bar and press Enter. Accept the warning that you’ll be careful. In the search box, type:
media.peerconnection.enabled
Double-click it to switch the value from true to false. That disables WebRTC entirely, closing the IP-leak path. The change takes effect immediately — no restart needed.
What the setting does
Setting media.peerconnection.enabled to false turns off WebRTC’s peer-connection capability, which is the part that can expose your real IP. Sites can no longer query your network addresses through it, so a VPN’s masking holds.
The trade-off
Because this disables WebRTC fully, browser-based calls that depend on it — some video conferencing and voice-chat sites — may stop working in Firefox. If you need those, you can toggle the setting back to true temporarily, or keep a separate browser profile for calls. For most privacy-focused browsing, leaving it off is fine.
A note on related settings
You may see other media.peerconnection.* entries. The single enabled toggle above is the one that matters for stopping leaks; you don’t need to change the others. Avoid changing unrelated about:config values unless you know what they do.
Confirm the fix
With your VPN active, run our WebRTC Leak Test in Firefox. With the setting off, WebRTC should expose nothing — a clean “no leak” result. Re-check after major Firefox updates, since preferences occasionally reset.
Related: Disable WebRTC in Chrome, Brave & Edge · WebRTC Leak Test