Technical guides for every NetTools.tech tool — what it does, how it works, how to read the results and how to troubleshoot — plus articles for system administrators, DevOps engineers and security professionals.
Tool guideDNS & Domains
How to find out whether your router, firewall or DNS server answers recursive queries for anyone on the internet, what the RA and AA flags mean, and how to close an open resolver.
Tool guideWeb & SEO Utilities
What Open Graph and Twitter Card tags are, how chat apps and social networks turn them into preview cards, and how to read and fix the results of the NetTools.tech Open Graph Checker.
Tool guideWeb & SEO Utilities
How the NetTools.tech Page Size Checker downloads a page and the resources it references, what transfer size and resource size mean, and how to use the breakdown to make pages lighter.
Tool guideSecurity & Testing
How secure random password generation works, how length and character sets translate into entropy bits, which settings to choose for accounts, Wi-Fi and service credentials, and how the NetTools generator avoids bias without sending anything to a server.
Tool guideSecurity & Testing
Why complexity rules mislead, how pattern-based estimators like zxcvbn judge passwords the way attackers do, how to read guess counts and cracking times, and how the Have I Been Pwned k-anonymity check works without sending your password.
Tool guideNetwork Diagnostics
What ping measures, how ICMP echo request and reply work, how to read RTT, TTL, loss and jitter, and why a host that ignores ping is not necessarily down.
Tool guideNetwork Diagnostics
How to check whether a TCP port accepts connections from the internet, what open, closed and filtered results mean, and how to troubleshoot port forwarding and firewalls.
Tool guideNetwork Diagnostics
How the NetTools.tech port scanner tests your own public IP or a DNS-verified server with fixed Nmap profiles, how to read open, closed and filtered ports, and what to do about exposed services.
Tool guideConversion & Calculation Tools
Usable capacity, efficiency, theoretical performance and fault tolerance for ten RAID levels, exactly as the NetTools.tech RAID Calculator models them — including unequal disks, vendor-specific levels and the failure simulator.
Tool guideWeb & SEO Utilities
What 301, 302, 303, 307 and 308 redirects mean, how the NetTools.tech Redirect Checker follows every hop with a chosen user agent, and how to fix loops, long chains and HTTPS downgrades.
Tool guideDNS & Domains
What PTR records are, how an IPv4 or IPv6 address becomes an in-addr.arpa or ip6.arpa name, who controls reverse DNS, and why it matters for mail servers and logs.
Tool guideWeb & SEO Utilities
How AI and search crawlers pick their robots.txt group, why a named group overrides User-agent: *, what Google-Extended really controls, and how to read the NetTools.tech Robots.txt LLM Policy Checker.
Tool guideWeb & SEO Utilities
How robots.txt groups, Allow/Disallow rules, wildcards and status codes work, and how to fetch, validate and test a robots.txt with the NetTools.tech Robots.txt Checker or by pasting it.
Tool guideWeb & SEO Utilities
What security.txt is, where it must live, which fields RFC 9116 requires, and how to read the NetTools.tech security.txt Checker’s field table and validation results.
Tool guideWeb & SEO Utilities
What the sitemaps.org protocol requires, how the NetTools.tech Sitemap Checker fetches or parses a sitemap, and how to read and fix the errors and warnings it reports.
Tool guideEmail Tools
What an SMTP test checks, how the banner, EHLO and STARTTLS exchange works, how to read the NetTools.tech SMTP Test session and certificate output, and what to do when a port is blocked.
Tool guideEmail Tools
What goes into an SPF record, how the NetTools.tech SPF generator assembles and validates it in your browser, and how to publish and verify the result without breaking legitimate mail.
Tool guideEmail Tools
What SPF is, how receivers evaluate v=spf1 records, how the NetTools.tech SPF Lookup expands includes and counts DNS lookups, and how to fix multiple records, +all and PermError.
Tool guideDNS & Domains
What an SSL/TLS certificate check verifies, how trust chains and subject alternative names work, how to read expiry, issuer and protocol details, and how to fix common certificate errors.
Tool guideIP & Network Utilities
How CIDR prefixes divide an address into network and host bits, how to calculate network, broadcast, usable range and host counts for IPv4 and IPv6, and how to avoid the classic off-by-one and wrong-boundary mistakes.
Tool guideConversion & Calculation Tools
How masks, prefixes and wildcards relate, how the NetTools.tech converter calculates network, broadcast and host ranges (with RFC 3021 /31), and how its equal and VLSM network splitter allocates aligned blocks.
Tool guideEmail Tools
How TLS-RPT reports reach you, what the _smtp._tls record must contain, how the NetTools.tech TLS-RPT Lookup validates it, and why you want it before enforcing MTA-STS.
Tool guideNetwork Diagnostics
How traceroute discovers the routers between two hosts, what the hop table, asterisks and timings mean, and how to use an online traceroute to locate path problems.
Tool guideConversion & Calculation Tools
What the NetTools.tech Unit Converter covers, how it converts exactly with fractions instead of floating point, how Unix timestamps are detected and how to read every result.