Free Network Diagnostic Tools for Sysadmins, Developers, and Security Teams
NetworkWhois provides a growing set of free network tools built for real-world troubleshooting. Run IP WHOIS lookups to identify ownership and allocation details, check reverse DNS (PTR) when you need hostname context, and verify whether an IP is listed on common spam blacklists. For email teams, you can validate domain authentication signals like MX, SPF, DKIM, and DMARC, and for operations work you can inspect SSL certificates and test IPv6 connectivity. Most tools are usable instantly and the outputs are designed to be easy to copy and share in tickets or incident channels.
Most Popular Tools
WHOIS IP Lookup
Find IP owner, ASN, and allocation details.
IP Blacklist Checker
Check if an IP is listed on DNSBL/RBLs.
Reverse DNS Lookup
Find PTR hostnames for IP addresses.
Email Validator
Check MX/SPF/DKIM/DMARC signals.
SSL Checker
Inspect cert chain, expiry, and hostname match.
Ping IPv6
Test IPv6 reachability and latency.
Who uses NetworkWhois?
Network Administrators
Troubleshoot DNS, check IP ownership, validate routing context.
Developers
Debug HTTPS/headers, validate configs, share results with teams.
Security Teams
Investigate suspicious IPs, review certs, analyze HTTP posture.
Email Operators
Validate MX/SPF/DKIM/DMARC, check blacklists, confirm PTR.
Why Choose NetworkWhois?
Fast Troubleshooting
Get useful signal quickly with tools designed for real incident workflows.
Security & Privacy
Tools are built to be safe to use—avoid sharing secrets whenever possible.
Global Coverage
Diagnose domains and IPs with global context and consistent outputs.
Free to Use
Enterprise-style checks without subscriptions or complicated setup.
Frequently Asked Questions
What is NetworkWhois?
NetworkWhois is a free collection of network diagnostic, security, email, and developer tools. You can run lookups like IP WHOIS and reverse DNS, validate configurations, and troubleshoot connectivity without installing anything.
Are these tools really free?
Yes. The core tools are free to use. Some advanced tools may require a free account, and those are clearly labeled with a “Login Required” badge.
Do I need an account to use the tools?
Most tools are available without registration. A small number of tools are gated to prevent abuse and protect infrastructure.
How accurate are the results?
Results come from authoritative sources where possible (DNS resolvers, WHOIS databases, live TLS handshakes). Accuracy depends on the upstream data and your network conditions.
What should I use for email deliverability issues?
Start with Email Validator to check MX/SPF/DKIM/DMARC signals, then run an IP Blacklist check and confirm reverse DNS (PTR) is correctly configured.
What’s the difference between WHOIS and reverse DNS?
WHOIS identifies ownership and allocation details for an IP range. Reverse DNS maps an IP to a hostname via PTR records and is commonly used for email reputation and server identity.