IP and network tools

How these tools work

Every tool on this page runs inside your own browser. When you type an address into the subnet calculator or the checker, the arithmetic is done by your device; nothing is sent to a server, so nothing can be logged or stored. Most tools keep working without a connection once the page has loaded. The two exceptions are the home page, which has to ask an outside service for your public address because your device does not know it, and the response test, which times small requests to this site.

Which tool do I need?

• "What is my IP?" The home page shows your public IPv4 and IPv6 addresses and the details your browser shares.
• "Is this address private or public?" Use Check an IP. It also catches mistyped addresses.
• Homework, exams or setting up a network: the subnet calculator, the CIDR table and the IP converter show the working, not just the answer.
• A long IPv6 address to tidy or compare: the IPv6 tool.
• "How long will this download take?" The download time calculator, which also turns Mbps into megabytes per second.
• "Is my connection laggy?" The response test times ten small requests and reports the delay and its steadiness.
• Reporting a problem to a website or developer: your user agent and your screen size are the two details they ask for first.
• Looking something up: port numbers and HTTP status codes are searchable lists in plain words.

A note on accuracy

The address arithmetic is tested against known answers. Readings that come from your browser, such as connection speed or memory, are rough estimates that browsers deliberately blur for privacy; each page says so where it applies. If a result looks wrong, please tell us through the contact page with the value you typed.