I don't think that it is possible to detect a pay wall beforehand. A content blocking extension like uBlock Origin might be able to detect it, but I don't think that it would be of much use as this is how a website works. If this is about exceeding a limit of articles you can read for free then you can usually clear cookies for this websites or use a Private Browsing mode window and close this window to clear its data to reset this count. ---- You can clear the Cache and remove the Cookies for websites that cause problems via the "3-bar" Firefox menu button (Settings), click the padlock icon (Clear cookies and site data) for the domain in the selected tab. "Remove the Cookies" for websites that cause problems: *Settings -> Privacy & Security<br>Cookies and Site Data: "Manage Data" "Clear the Cache": *Settings -> Privacy & Security<br>Cookies and Site Data -> Clear Data -> [X] Cached Web Content -> Clear *https://support.mozilla.org/en-US/kb/clear-cookies-and-site-data-firefox *https://support.mozilla.org/en-US/kb/how-clear-firefox-cache