Internet and website troubleshooting guides
Search for an exact error code or symptom, find out what it means, what you can safely try, and whether the cause lies with your network, provider or website owner.
Browser error codes
Chrome, Edge, DNS and TLS
GuideERR_NAME_NOT_RESOLVED: what it means and how to fix itChrome shows ERR_NAME_NOT_RESOLVED? Check DNS, domain, local cache and network, and distinguish a public DNS issue from a problem on one device.GuideERR_CONNECTION_TIMED_OUT: meaning and fixesERR_CONNECTION_TIMED_OUT means a connection did not respond in time. Check the website, firewall, VPN, network and server reachability.GuideERR_EMPTY_RESPONSE: what it means when a page sends no dataLearn what ERR_EMPTY_RESPONSE means and distinguish server, proxy, TLS and local network issues.GuideERR_NETWORK_CHANGED: what it means and how to fix itERR_NETWORK_CHANGED occurs when a device switches or loses its network while loading a page. Check Wi-Fi, VPN, Ethernet and unstable connectivity.GuideERR_SSL_PROTOCOL_ERROR: meaning and HTTPS troubleshootingERR_SSL_PROTOCOL_ERROR means Chrome could not establish a valid HTTPS/TLS session. Check the certificate, TLS, proxy, CDN and HTTPS inspection.GuideNET::ERR_CERT_DATE_INVALID: what it means and how to fix itChrome NET::ERR_CERT_DATE_INVALID: check your device clock and TLS certificate validity. Steps for visitors and website owners.GuideERR_TOO_MANY_REDIRECTS: how to fix redirect loopsFind out what ERR_TOO_MANY_REDIRECTS means, what visitors can do and how owners diagnose loops involving HTTP, HTTPS, www, CDN or login.GuideERR_CONNECTION_REFUSED: what it means and how to fix itUnderstand ERR_CONNECTION_REFUSED and determine whether the problem is the website, server, network, proxy, VPN or local device.
Reference
All codes →HTTP status codes: 500, 503, 429, 522…
500Internal Server ErrorUnexpected server error.503Service UnavailableThe server is temporarily unavailable.429Too Many RequestsToo many requests; wait and retry.401UnauthorizedA login or token is required.400Bad RequestMalformed request.301Moved PermanentlyPermanent redirect.522Cloudflare: Connection Timed OutThe origin didn't respond in time.521Cloudflare: Web Server Is DownThe origin refused the connection.
Website errors
HTTP, DNS and certificates
Guide404 Not Found: what it means and how to fix itLearn what 404 Not Found means, why it appears and what visitors or website owners can do.Guide403 Forbidden: what does it mean?403 Forbidden means the server understood a request but denied access. Explore common causes and safe troubleshooting steps.Guide502 Bad Gateway: what does it mean?Understand 502 Bad Gateway, where it occurs, why it is often temporary and how to diagnose it.GuideDNS_PROBE_FINISHED_NXDOMAIN: meaning and fixesLearn what DNS_PROBE_FINISHED_NXDOMAIN means and distinguish a mistyped address, DNS issue or domain configuration problem.GuideYour connection is not private — what should you do?What the browser's 'Your connection is not private' warning means and when you must not proceed.
Home networks
Wi-Fi, ping and CGNAT
GuideWhy is my Wi-Fi slow?Slow Wi-Fi is not always slow internet. Check signal, band, congestion, devices, router and subscription systematically.Guide2.4 GHz or 5 GHz Wi-Fi?Compare 2.4 and 5 GHz Wi-Fi range, speed, obstacles, interference and practical usage.GuideWhat is ping and what is a good response time?Ping measures latency, not throughput. Understand milliseconds, jitter and packet loss.GuideWhat is CGNAT?CGNAT lets ISPs share a public IPv4 address among customers. Understand the effects on port forwarding and remote access.
Security and email
Phishing, online stores and authentication
GuideHow to spot phishingPractical phishing warning signs: domains, urgency, login pages, attachments, payments and safer verification steps.GuideHow to check an online store before buyingTechnical and business warning signs to evaluate an unfamiliar online store before making a purchase. No single indicator proves legitimacy.GuideSPF, DKIM and DMARC: what's the difference?An accessible guide to SPF, DKIM and DMARC, what each mechanism checks, how they work together, the DNS records needed and common mistakes.