Private & Reserved IP Ranges
The RFC 1918 private ranges plus the other special-use IPv4 and IPv6 blocks you should never route on the public internet — with a live checker that tells you exactly which range any IPv4 address falls into.
IPv4 special-use ranges
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IPv6 special-use ranges
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Not every IP address is meant to travel the open internet. Whole blocks are set aside by the IETF for private networks, loopback, documentation, link-local auto-configuration and future use. Knowing these ranges tells you at a glance whether an address is a real public host or something that only means anything inside a local network.
The best known are the three RFC 1918 private ranges: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. Your home router almost certainly hands out addresses from 192.168.0.0/16, while large corporate networks favour 10.0.0.0/8 for its 16 million addresses. These are reused by countless networks worldwide because they are never routed publicly — a device only reaches the internet when NAT rewrites its private address into a shared public one.
10.0.0.0/8 is private — usable for your own hosts. 127.0.0.0/8 is loopback — it always means "this machine". 169.254.0.0/16 is link-local — a self-assigned fallback when DHCP fails. Seeing a 169.254 address is usually a sign that something went wrong on the network.
Beyond the private blocks, several ranges are reserved for special jobs: 100.64.0.0/10 for carrier-grade NAT, the 192.0.2.0/24, 198.51.100.0/24 and 203.0.113.0/24 documentation ranges you will see in examples and RFCs, 224.0.0.0/4 for multicast, and 240.0.0.0/4 reserved for future use. IPv6 has its own equivalents, including ::1/128 loopback, fc00::/7 unique local addresses and fe80::/10 link-local.
For the bigger picture, read Reserved IP addresses and Public vs private IP addresses. To work with these blocks directly, try our IP-in-Subnet Checker and Subnetting Cheat Sheet.
Frequently asked questions
What are the private IP address ranges?
RFC 1918 defines three private IPv4 ranges: 10.0.0.0/8 (10.0.0.0–10.255.255.255), 172.16.0.0/12 (172.16.0.0–172.31.255.255) and 192.168.0.0/16 (192.168.0.0–192.168.255.255). These are reused freely inside private networks and are never routed on the public internet.
Why can't private IP addresses be reached from the internet?
Private ranges are non-routable on the public internet by agreement, so ISPs and routers drop them. Millions of separate networks reuse the same private addresses, so there is no way to tell them apart globally. Devices reach the internet through NAT, which swaps their private address for a shared public one.
What is 169.254.x.x used for?
169.254.0.0/16 is the link-local range, also called APIPA on Windows. A device assigns itself an address here automatically when it cannot reach a DHCP server, so a 169.254 address usually means DHCP failed.
Is 127.0.0.1 a private address?
127.0.0.1 is the loopback address, part of the reserved 127.0.0.0/8 block. It always refers to the local machine and never leaves the device, so it is a special-purpose reserved address rather than a private (RFC 1918) one.
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