About TCPLab

What is TCPLab?

TCPLab is a free online network toolbox for developers, sysadmins and anyone who wants to see how the internet looks from the outside. Every tool runs a real measurement from our own servers or from your browser — no sign-up, no installation, and no stored query history.

What you can do

• IP lookup — geolocation, ISP and network type for any IPv4/IPv6 address or domain, with a batch mode for up to 50 addresses.
• DNS lookup (dig) — query A, AAAA, CNAME, MX, TXT and NS records with TTL and response time.
• HTTP status check — inspect status codes, response headers and redirect targets without downloading the page body.
• TCP port check — test whether a port is open on any host.
• China & global IP check — compare the egress IP used for domestic and international traffic.
• GFW check — probe a target from a mainland China node and an overseas node to spot blocking.

How it works

Tools that need a server-side measurement run from our own infrastructure. Browser-side checks, such as the China & global IP check, are sent straight from your device. The IP geolocation databases are bundled offline (ip2region, GeoCN and MaxMind GeoLite2), so lookups never call a third-party API.

Privacy by default

We do not store the content of your queries. The addresses and domains you enter are used to run the check and then discarded. See our Privacy Policy for the details.

Contact

Questions, bug reports or partnership requests are welcome at support@tcp.lc.