What does `link-local` mean?

An address that's only valid inside a single network segment. IPv4 uses 169.254.0.0/16 when a host fails to get a DHCP lease; IPv6 uses fe80::/10 for neighbour discovery and is set automatically by every interface.

Why are 192.0.2.0, 198.51.100.0, and 203.0.113.0 listed as documentation?

RFC 5737 reserves those three /24 blocks (and 2001:db8::/32 for IPv6) for examples in documentation and training material — they're guaranteed never to appear on the public internet, which makes them safer than picking a real-looking IP that might exist.

What's the reverse-DNS form for?

DNS PTR records — they map an IP back to a hostname. IPv4 reverses the octets and appends `.in-addr.arpa`; IPv6 reverses every hex nibble and appends `.ip6.arpa`. The reverse zones are delegated to whoever owns the address space.

IP Address Inspector

Parses a single IP, classifies it (Class A–E for v4; global / link-local / loopback / unique-local / multicast / documentation for v6), and shows every notation you commonly need to paste somewhere: decimal, hex, binary, the IETF `in-addr.arpa` / `ip6.arpa` reverse-DNS form, and the /32 (or /128) CIDR.

—

IP address

VersionIPv4
Scopeprivate
ClassClass C
Decimal3232235818
Hex0xC0A8012A
Binary11000000.10101000.00000001.00101010
CIDR (/32)192.168.1.42/32
Reverse DNS42.1.168.192.in-addr.arpa

For CIDR ranges, use the Subnet Calculator instead — this tool focuses on single addresses.

How to use

Type or paste an IPv4 (`192.168.1.1`) or IPv6 (`fe80::1`, `2001:db8::1`) address.
Read the scope and class to know what you're looking at.
Copy the form you need — reverse DNS for PTR records, decimal for a packed integer, binary for subnetting math.

Frequently asked questions

What does `link-local` mean?: An address that's only valid inside a single network segment. IPv4 uses 169.254.0.0/16 when a host fails to get a DHCP lease; IPv6 uses fe80::/10 for neighbour discovery and is set automatically by every interface.
Why are 192.0.2.0, 198.51.100.0, and 203.0.113.0 listed as documentation?: RFC 5737 reserves those three /24 blocks (and 2001:db8::/32 for IPv6) for examples in documentation and training material — they're guaranteed never to appear on the public internet, which makes them safer than picking a real-looking IP that might exist.
What's the reverse-DNS form for?: DNS PTR records — they map an IP back to a hostname. IPv4 reverses the octets and appends `.in-addr.arpa`; IPv6 reverses every hex nibble and appends `.ip6.arpa`. The reverse zones are delegated to whoever owns the address space.

Guides on this topic

IP Addresses and Subnets, Without the Hand-Waving What an IP address really is, how to read CIDR notation and count the hosts in a prefix, which ranges must never be routed, how IPv6 changes the arithmetic, and why sorting addresses as text goes wrong.

Related tools

IPv4 Address Converter

Convert an IPv4 address between dotted-decimal, 32-bit integer, hex and binary — and see whether it's private, public, loopback and more.

Network 0 0

CIDR Aggregator (Merge & Summarize IP Ranges)

Coalesce a messy list of IPv4/IPv6 addresses, CIDR blocks, and ranges into the smallest equivalent set of CIDR prefixes.

Network 0 0

Random IP & MAC Generator

Generate batches of random IPv4, IPv6, or MAC addresses for tests and mocks — public / private / ULA / link-local / UAA / LAA scopes supported.

Random 0 0

Subnet Calculator (IPv4 / CIDR)

Parse an IPv4 CIDR into network address, broadcast, netmask, wildcard, host range, and class. Shows binary breakdown and private/public status.

Network 0 0

MAC Address Formatter

Reformat a MAC address between colon, hyphen, Cisco dot and no-separator notation, in upper or lower case — and see its unicast/multicast and universal/local type.

Network 0 0

IP Range Expander

Expand a CIDR block (10.0.0.0/24) into a list of IPs, or convert a start-end range into the smallest covering CIDR set. Shows network, broadcast, mask, wildcard, usable count — all in the browser.

Network 0 0