DNS, SSL & Network Troubleshooting Guides

Free guides and tutorials for DNS, SSL, networking, and web security.

IPv4 vs IPv6 comparison of address size, header, NAT and our measured connection times to eight dual-stack sites

IPv4 vs IPv6: Key Differences, Speed Test & Which to Use

IPv4 vs IPv6 explained: 32-bit vs 128-bit addresses, headers, NAT, security and adoption, plus our speed test of 8 sites over both. Which should you use?

Oct 410 min read

Diagram of how a DNS server resolves a domain through root, TLD and authoritative nameservers with real timings

What Is a DNS Server? How It Works, Types & Examples

A DNS server turns domain names into IP addresses. See how one resolves a name step by step, the 4 types of DNS servers, how to find yours and which to use.

Oct 411 min read

Cloudflare DNS servers 1.1.1.1 and 1.0.0.1 with IPv6 addresses, Families filters and DoH/DoT endpoints

Cloudflare DNS Servers: 1.1.1.1 IPs, IPv6 & Setup Guide

Cloudflare DNS servers are 1.1.1.1 and 1.0.0.1 (IPv6 2606:4700:4700::1111). Get every address, the Families filters, DoH/DoT and setup steps for each device.

Oct 310 min read

Google DNS servers 8.8.8.8 and 8.8.4.4 with IPv6 addresses and dns.google DoH/DoT endpoints

Google DNS Servers: 8.8.8.8, 8.8.4.4 & IPv6 Setup Guide

Google DNS servers are 8.8.8.8 and 8.8.4.4 (IPv6 2001:4860:4860::8888). Get every address, DoH/DoT, what Google logs and the setup steps for each device.

Oct 310 min read

.si domain guide: new .si registrations jumped from 3,515 in August to 46,066 in September 2026, with key .si registration rules

.si Domain: Why It's Trending & How to Register One (2026)

The .si domain is Slovenia's ccTLD and, since September 2026, shorthand for "super intelligence". Who can register .si, the rules, prices, the SEO catch and how to buy one.

Oct 29 min read

400 Bad Request: Request Header Or Cookie Too Large nginx page with the fixes to try in order

400 Bad Request: What It Means & How to Fix It

400 Bad Request means the server couldn't understand the request your browser sent. Fix it in a minute (URL, cookies, cache) or on your server (header limits).

Sep 309 min read

405 Not Allowed nginx error page next to the step-by-step fixes for 405 Method Not Allowed

405 Method Not Allowed: What It Means & How to Fix It

405 Method Not Allowed means the server knows the URL but won't accept that HTTP method there. Fix it in nginx, IIS, Next.js, Flask or your API calls.

Sep 308 min read

502 Bad Gateway nginx error page beside the five checks that fix most 502 errors

502 Bad Gateway: What It Means & How to Fix It

502 Bad Gateway means a proxy got a bad reply from the server behind it. Fix it as a visitor in a minute, or as a site owner with nginx, PHP-FPM and Node logs.

Sep 3011 min read

Error 520 Web server is returning an unknown error page with the origin checks that fix it

Cloudflare Error 520: What It Means & How to Fix It

Cloudflare error 520 means your origin server sent Cloudflare an empty or unexpected reply. Find the cause (crashes, blocked IPs, big headers) and fix it fast.

Sep 308 min read

Chrome showing 192.168.1.1 is unreachable with ERR_ADDRESS_UNREACHABLE and the fixes to try

ERR_ADDRESS_UNREACHABLE: What It Means & How to Fix It

ERR_ADDRESS_UNREACHABLE means your device has no route to that IP, often a router, NAS or camera. Fix it on Mac, Windows, Android and iPhone in a few steps.

Sep 309 min read

Chrome error page: example.com unexpectedly closed the connection, ERR_CONNECTION_CLOSED, with fixes

ERR_CONNECTION_CLOSED: What It Means & How to Fix It

ERR_CONNECTION_CLOSED means the server or something in between hung up, usually mid HTTPS handshake. Fix it on your device, or on your server's TLS setup.

Sep 309 min read

ERR_CONNECTION_RESET error screen in Chrome next to the five fixes to try, in order

ERR_CONNECTION_RESET: What It Means & How to Fix It

ERR_CONNECTION_RESET means a TCP reset cut your connection mid-load. Find who sent it and fix it on Windows, Mac, Android, iPhone, or your own web server.

Sep 3010 min read