Using Google search, I presume? I think this problem is caused by older router firmware that doesn't support IPv6 addresses. If your router has an update available, that would be the best approach: https://www.reddit.com/r/firefox/comments/hmc3t0/google_search_forcing_captcha_dialog_6to4_tunnel/ If not, you could try disabling Firefox from using IPv6 addresses: (1) In a new tab, type or paste '''about:config''' in the address bar and press Enter/Return. Click the button accepting the risk. (2) In the search box in the page, type or paste '''ipv''' and pause while the list is filtered ''Experiment #1:'' (3) Double-click the '''network.dns.ipv4OnlyDomains''' preference to display an editing field, and enter ''www.google''.''com'' (or your actual Google search site if you use a different one) then press Enter or click the blue check mark button to save the change. You may need to clear cache to make sure Firefox requests a new address: [[How to clear the Firefox cache]] (this should be limited to cache and not include cookies/history) ''Experiment #2 (if #1 doesn't work):'' (4) Double-click the '''network.dns.disableIPv6''' preference to switch the value from false to true (You may need to clear cache to make sure Firefox requests a new address) Does that work? Please let us know because this question is coming up more often in recent days. Thanks.