net::ERR_SSL_PROTOCOL_ERROR

Ssl Protocol Error triggered by browser extensions is one of the hardest categories to diagnose because it disappears when you open DevTools (some extensions pause when DevTools is open) or test in a different browser profile. Ad blockers (uBlock Origin, AdBlock Plus) and privacy tools (Privacy Badger, Ghostery) use filter lists that block requests matching patterns associated with tracking. If your legitimate API endpoint or script URL matches a filter rule, it is silently blocked — the browser reports a network error similar to Ssl Protocol Error. Test in a clean profile without any extensions using Chrome's guest mode or Firefox's Private Browsing. If the error disappears, use the extension's logger to identify which rule is blocking the request. The fix for production: rename URLs that inadvertently match tracking patterns (e.g., avoid /analytics, /track, /pixel in API paths), or proxy third-party resources through your own domain to prevent filter list matching. Firefox's Enhanced Tracking Protection similarly blocks third-party requests — check the shield icon in the address bar for blocked content.