IP Address Parser

Runs in browser Web

Parse IPv4 and IPv6 addresses, expand or compress IPv6, compute CIDR network/broadcast/host counts, detect private, loopback, link-local and reserved ranges, and convert between decimal, binary and hex.

Privacy: This tool runs entirely in your browser. Your input never leaves your device.

What is an IP address, and what does CIDR notation mean?

An IPv4 address is 32 bits written as four decimal octets (192.168.1.10); an IPv6 address is 128 bits written as eight hexadecimal groups with :: compressing runs of zeros. CIDR notation adds a prefix length — 10.0.0.0/8 — that says how many leading bits identify the network, which is how firewall rules, allow-lists and subnets are expressed. RFC 1918 reserves the private ranges that never appear on the public Internet.

In 192.168.1.130/26 the first 26 bits name the network and the last 6 number 64 addresses; the first and last are reserved, leaving 62 hosts.

192.168.1.130 as 32 bits

Octets

192 168 1 130

Bits

11000000 10101000 00000001 10000010

Network / host bits

26 6

Netmask /26

255 255 255 192

Last octet of 192.168.1.128/26: 64 addresses

Axis from 128 to 191
  • 128–19164 addresses
  • 129–19062 usable hosts
  1. 1192.168.1.128 Network addressHost bits all 0; the tool normalises the input to 192.168.1.128/26
  2. 2192.168.1.130 Your inputHost bits 000010 are not all 0, so it is not the network address
  3. 3192.168.1.191 Broadcast addressHost bits all 1

/31 and /32 are exceptions: RFC 3021 point-to-point links use both addresses, and /32 is one host. IPv6 splits 128 bits the same way but has no broadcast, so the tool counts every address as usable.

How to use IP Address Parser

  1. Enter an address (10.0.0.1, 2001:db8::1), a CIDR range (10.0.0.0/22) or an integer.
  2. Read the address card for scope and routability, and the CIDR card for the subnet layout.
  3. Use the membership field to test whether another address falls inside the range.

IP Address Parser features

  • IPv4 and IPv6 validation with precise error messages (out-of-range octet, leading zeros, double "::", bad group)
  • IPv6 expansion and RFC 5952 compression, zone identifiers (fe80::1%eth0) and IPv4-mapped addresses
  • CIDR maths with BigInt: network, broadcast, first/last host, netmask, wildcard mask, total and usable addresses
  • Classification: private, loopback, link-local, multicast, CGNAT, documentation, benchmarking, unique-local, 6to4, Teredo, reserved, public
  • Conversions to decimal, hexadecimal, binary and reverse-DNS (in-addr.arpa / ip6.arpa) names
  • Integer and hex input converted back to addresses; membership check of an address in a range

IP Address Parser example

Subnet a /26

Input:

192.168.1.130/26

Output:

CIDR: 192.168.1.128/26 (normalised — host bits were set)
Network: 192.168.1.128 · Broadcast: 192.168.1.191
First host: 192.168.1.129 · Last host: 192.168.1.190
Netmask: 255.255.255.192 · Wildcard: 0.0.0.63
Total: 64 · Usable: 62 · Scope: Private network (RFC 1918)

Frequently asked questions about IP Address Parser

How many usable hosts does a /26 have?

64 addresses, of which 62 are usable: the first is the network address and the last the broadcast address. /31 networks are the exception (RFC 3021 point-to-point links use both addresses) and /32 is a single host.

How is an IPv6 address compressed?

Following RFC 5952: leading zeros in each group are dropped, the longest run of two or more zero groups is replaced by "::" (the first one if there is a tie), and hex digits are lower-case. The tool shows both the expanded and the canonical form.

Which ranges are private?

IPv4: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 (RFC 1918), plus 100.64.0.0/10 for carrier-grade NAT. IPv6: fc00::/7 unique local addresses. Link-local ranges are 169.254.0.0/16 and fe80::/10; loopback is 127.0.0.0/8 and ::1.

Can I convert an integer back to an IP?

Yes. Enter a plain decimal such as 3232235777 (→ 192.168.1.1) or a hexadecimal value such as 0xC0A80101; large integers are interpreted as IPv6.

How do I check whether an address is inside a range?

Enter the CIDR range (e.g. 10.20.0.0/16) as the main input and the address to test in the "Check membership" field.

Technical notes

All arithmetic uses 128-bit BigInt values so IPv6 prefixes such as /48 (2^80 addresses) are exact. Special-purpose ranges come from the IANA IPv4 and IPv6 Special-Purpose Address Registries (RFC 6890 and successors), including the 2024 documentation prefix 3fff::/20.

References