Network Error Code Reference

Encountering a network error? Search this comprehensive reference of browser, operating system, and protocol error codes. Each entry explains what the error means, what causes it, and how to fix it.

Search Error Codes

Error Code	Cause	Fix

Understanding Network Error Codes

Network error codes are diagnostic messages returned by browsers, operating systems, and networking software when a connection fails. Unlike HTTP status codes (which come from the server), network errors indicate that the connection itself couldn't be established or was interrupted before any HTTP response was received.

These errors originate from different layers of the OSI model: DNS errors occur at the Application layer when name resolution fails, connection errors happen at the Transport layer when TCP can't establish a connection, and SSL errors occur during the TLS handshake. Understanding which layer an error belongs to helps you troubleshoot effectively.

Most Common DNS Errors

DNS errors prevent your browser from finding the server's IP address. They're among the most frequent network issues:

Error	What Happened	Quick Fix
`DNS_PROBE_FINISHED_NXDOMAIN`	Domain doesn't exist in DNS	Check URL, flush DNS, try 8.8.8.8
`DNS_PROBE_FINISHED_NO_INTERNET`	No internet for DNS resolution	Check connection, restart router
`ERR_NAME_NOT_RESOLVED`	DNS lookup failed	Flush DNS, change DNS server

For DNS troubleshooting, use our DNS Lookup to verify domain resolution. If DNS issues persist, see our guide on fixing DNS server not responding and how to change DNS on your router.

Pro Tip: Most DNS errors can be fixed by flushing your DNS cache (ipconfig /flushdns on Windows, sudo dscacheutil -flushcache on Mac) and switching to a reliable public DNS like Google (8.8.8.8) or Cloudflare (1.1.1.1). You can change DNS on your router to apply this fix to all devices on your network. For encrypted DNS, consider enabling DNS over HTTPS.

Connection Errors Explained

Connection errors mean the TCP connection to the server couldn't be established or was interrupted:

Error	OSI Layer	Usual Cause	Diagnostic Tool
`ERR_CONNECTION_REFUSED`	Transport (4)	Server not listening on port	Port Checker
`ERR_CONNECTION_RESET`	Transport (4)	Connection forcibly closed	Ping Test
`ERR_CONNECTION_TIMED_OUT`	Network (3)	Server unreachable or too slow	Ping Test
`ERR_INTERNET_DISCONNECTED`	Physical (1-2)	No network connection	Check cables/WiFi
`ERR_ADDRESS_UNREACHABLE`	Network (3)	IP routing failure	IP Lookup

SSL/TLS Error Troubleshooting

SSL errors occur during the HTTPS encryption handshake. They indicate certificate or encryption problems:

ERR_CERT_DATE_INVALID — Certificate expired or system clock wrong. First check your computer's date/time. If correct, the site needs to renew its certificate. Verify with our SSL Certificate Checker.
ERR_CERT_AUTHORITY_INVALID — Self-signed or untrusted CA certificate. Common on internal/dev sites. The site needs a certificate from a trusted CA.
ERR_SSL_PROTOCOL_ERROR — TLS version or configuration mismatch. Disable antivirus SSL scanning. Clear SSL state in browser settings.
ERR_CERT_COMMON_NAME_INVALID — Certificate doesn't match the domain. The site needs a certificate covering the exact domain you're visiting.

Note: Never bypass SSL certificate warnings for sensitive sites (banking, email, etc.). These warnings exist to protect you from man-in-the-middle attacks. If you see SSL errors on sites that normally work, check if your network has a captive portal, transparent proxy, or if someone is intercepting your traffic. Ensure your home WiFi is secured and your router firmware is updated.

General Troubleshooting Workflow

Check your connection — Can you reach other websites? Test with our Speed Test.
Test DNS — Use our DNS Lookup to verify the domain resolves.
Ping the server — Use our Ping Test to check if the server responds.
Check ports — Use our Port Checker to verify the service port is open.
Verify SSL — Use our SSL Certificate Checker for HTTPS issues.
Check your IP — Use What Is My IP to confirm your connection is active.

If you're accessing your router's admin panel and getting errors, make sure you're connected to the router's network and using the correct gateway IP address.

Fixing Common Errors by Platform

Platform	Flush DNS	Reset Network
Windows	`ipconfig /flushdns`	`netsh winsock reset`
macOS	`sudo dscacheutil -flushcache`	System Preferences → Network → Advanced → Reset
Linux	`sudo systemd-resolve --flush-caches`	`sudo systemctl restart NetworkManager`
Chrome	`chrome://net-internals/#dns` → Clear	`chrome://net-internals/#sockets` → Flush

Key Takeaways

Network errors differ from HTTP status codes — they indicate connection failures, not server responses.
DNS errors (NXDOMAIN, NAME_NOT_RESOLVED) are the most common and usually fixed by flushing DNS cache or changing DNS server.
Connection errors indicate TCP-level issues — check if the server and port are accessible.
SSL errors indicate certificate or encryption problems — never bypass warnings on sensitive sites.
Use the diagnostic workflow: check connection → test DNS → ping server → check ports → verify SSL.
Our DNS Lookup, Ping Test, and Port Checker tools help diagnose each error type.

Video: How to Fix Common Network Errors

Related Tools and Guides

Frequently Asked Questions

What does DNS_PROBE_FINISHED_NXDOMAIN mean?

This error means the domain name you're trying to visit does not exist in DNS (NXDOMAIN = Non-Existent Domain). It's usually caused by a typo in the URL, a domain that hasn't been registered, or DNS misconfiguration. Try checking the spelling, flushing your DNS cache, or switching to a different DNS server like Google (8.8.8.8).

How do I fix ERR_CONNECTION_REFUSED?

ERR_CONNECTION_REFUSED means the server is not accepting connections on the requested port. The web server may be down, a firewall may be blocking the port, or the service may be running on a different port. Use a port checker to verify the port is open and accessible.

Why do I keep getting ERR_CONNECTION_TIMED_OUT?

This error means your browser waited too long for the server to respond. Common causes include: server being down, firewall blocking the connection, network issues between you and the server, or DNS resolution taking too long. Check your internet connection first, then try pinging the server directly.

What causes SSL certificate errors?

SSL errors are caused by: expired certificates, self-signed certificates, certificate domain mismatches, untrusted certificate authorities, or incorrect system date/time. Check your system clock first, then verify the certificate with an SSL checker. Never bypass SSL warnings on sensitive websites.

How do I fix DNS errors in Chrome?

In Chrome: clear the DNS cache at chrome://net-internals/#dns, flush your system DNS cache, change your DNS server to 8.8.8.8 or 1.1.1.1, and restart Chrome. If errors persist, try disabling browser extensions or testing in incognito mode.

What is the difference between a network error and an HTTP error?

A network error (like ERR_CONNECTION_REFUSED) means the connection to the server couldn't be established at all — no HTTP response is received. An HTTP error (like 404 or 500) means the connection succeeded but the server returned an error response. Network errors are typically more serious and indicate infrastructure or connectivity issues.

About Tommy N.

Tommy is the founder of RouterHax and a network engineer with 10+ years of experience in home and enterprise networking. He specializes in router configuration, WiFi optimization, and network security. When not writing guides, he's testing the latest mesh WiFi systems and helping readers troubleshoot their home networks.