Articles & Guides
Useful resources for web developers and system administrators
Networking
192.168.1.1 Router Login: Find the IP, Sign In, Fix Errors
How to log in to your router at 192.168.1.1: find the real gateway IP on any OS, default logins by brand and ISP, and a fix table for when the page won't load.
Security
Russia's Personal Data Operators Registry: Check and File
How Roskomnadzor's personal data operators registry works: who must notify under 152-FZ Article 22, how to search by INN, and how to file or update an entry.
Security
OSINT for Domains and Websites: What to Check and How
OSINT for websites explained: what WHOIS/RDAP, DNS, crt.sh certificate logs, IP and ASN data, reverse IP and the Wayback Machine reveal, with commands and tools.
DNS
nslookup Command: How to Use It and Read the Output
How to use nslookup on Windows, Linux and macOS: query a specific DNS server, look up MX, TXT, NS and SOA records, read the output and fix common errors.
Infrastructure
IMAP vs POP3: Differences, Ports and Which One to Use
IMAP keeps mail on the server and syncs every device; POP3 downloads it to one computer. Comparison table, ports 993 and 995, provider settings and test commands.
Domains
Example.com: What It Is and Which Domains to Use for Testing
Example.com is an IANA-reserved domain for documentation (RFC 2606). Why it has no email, what .test, .invalid and .localhost do, and which names to use in tests.
Networking
ERR_FAILED in Chrome: What It Means and How to Fix It
ERR_FAILED is Chromium's generic network error. Learn how it differs from ERR_CONNECTION_FAILED and the proxy errors, and fix proxy, extension and site-data causes.
Domains
Domain Owner Lookup: Who Owns a Domain, Its Age and History
How to find who owns a domain with WHOIS and RDAP, what GDPR redaction hides, how to reach a private owner, and how to read domain age, registrar and history.
DNS
DNS Server Not Responding: How to Fix It on Windows and More
DNS server not responding? Find the cause by symptom and fix it: router reboot, flushdns, Winsock reset, public DNS like 1.1.1.1, nslookup tests, macOS and Linux.
SSL/TLS
Your Connection Is Not Private: What It Means and How to Fix It
“Your connection is not private” explained: what each NET::ERR_CERT code means, how to fix it on your device or server, and when it is safe to proceed.