Free Network Tools — DNS, WHOIS, IP & SSL Lookup
Diagnostic tools for domains, addresses and certificates: look up DNS records, check propagation across resolvers worldwide, query WHOIS and RDAP registration data, geolocate an IP, test whether an address is blacklisted, inspect TLS certificates and HTTP headers, and check whether a port is reachable.
These are the checks you reach for when email stops delivering, a site shows a certificate warning, or a DNS change doesn't seem to have taken effect. All free, with no account required.
📍 IP5
What's My IP
Show your public IP, location, ISP and browser instantly.
IP Address Lookup
Locate any IP — geo, ISP, ASN and reverse DNS.
IP Blacklist Check
Check if an IP is on spam blacklists (DNSBL).
Reverse DNS Lookup
Turn an IP address into its PTR hostname.
User Agent Parser
Decode a user-agent into browser, OS and device.
🌐 DNS2
🏷 Domain3
🔒 SSL4
SSL Certificate Checker
Check a site's TLS cert: trust, hostname match, expiry.
Certificate Decoder
Decode a PEM certificate — subject, SANs, expiry, fingerprints.
CSR Decoder
Decode a Certificate Signing Request before you submit it.
Certificate Key Matcher
Check a certificate, private key & CSR belong together.
More Networking tools
What's included
- DNS — record lookup (A, AAAA, MX, TXT, NS, CNAME, SOA) with TTL, plus a global propagation checker across ~20 resolvers.
- Domain — WHOIS with explained status codes, structured RDAP, and an availability checker.
- IP — What's My IP, IP geolocation lookup, reverse DNS, DNSBL blacklist check and user-agent parsing.
- SSL/TLS — certificate checker for trust, hostname match and expiry, plus certificate, CSR and key-matching decoders.
- HTTP — response header inspection and TCP port reachability testing.
Common problems these solve
- Email landing in spam — check your sending IP against blacklists and confirm reverse DNS.
- A DNS change that hasn't taken effect — see which resolvers worldwide still return the old value.
- Browser certificate warnings — verify chain trust, hostname match and expiry.
- Investigating suspicious traffic — trace an IP's location, provider and network.
Frequently asked questions
Are these network tools free?
Yes, all of them, with no signup or account required.
Why do DNS results differ between tools?
Different resolvers cache records for different lengths of time based on TTL. That's exactly what the propagation checker shows — the same record as seen from resolvers around the world.
Why does WHOIS hide the owner's contact details?
Privacy rules such as GDPR, along with paid WHOIS privacy services, redact personal contact information. Registrar, dates, nameservers and status codes remain visible.
Do the certificate tools upload my files?
No. The certificate, CSR and key decoders parse everything locally in your browser — only the live site checker connects out, and that's to the site you name.