Any inaccuracies in this index may be explained by the fact that it has been sorted with the help of a computer. --Donald Knuth

What is an IP Address?


An IP address uniquely identifies a computer or other device on the internet.

Find out what your current IP address is.

What is an IP Address?

An IP address uniquely identifies your computer on the internet among all the other computers throughout the world or if your computer is not connected to the internet it uniquely identifies your computer among all the others on your local network.

IP addresses all have the same form: a series of numbers separated by a dot such as IP addresses typically consist of 4 numbers. Each of the 4 numbers is between 0 and 255. The numbers are sometimes called octets because in binary form they are each represented by a series of 8 bits or 1 byte of data.

Most IP addresses today contain only 4 numbers. But we eventually discovered this wasn't going to be enough. One octect will allow you up to 255 different numbers. Two octects (255.255) will allow you to have 255^2 unique combinations, or 65,025. Three octects (255.255.255) allows you to have 255^3 or 16 million. And finally 4 octects allows more than 4 billion combinations. You would think that would be enough, but clearly if every person on Earth had a computer we'd run out of IP addresses. So, IPv6 is developing, an IP standard containing 6 octects or 275 trillion possible combinations. Maybe that will get us by for a while.

With the growth of the internet and the realization that in the not too distant future, your car, microwave, refrigerator, cell phone and VCR may each have their own IP address, we will quickly surpass 4 billion IPs and IPv6 will become ubiquitous.