IPv6 notation tool

Expand IPv6 address 21:db8::2:1

Write any valid IPv6 address in its complete eight-group form for subnetting, binary analysis, logs, and documentation.

Example: 2001:db8::1

The conversion runs locally and does not use an external lookup service.

Expansion result

Full IPv6 notation for 21:db8::2:1

Expanded IPv6 address

0021:0db8:0000:0000:0000:0000:0002:0001

Compressed IPv6

21:db8::2:1

Expanded IPv6

0021:0db8:0000:0000:0000:0000:0002:0001

IPv6 groups

8 groups of 4 hexadecimal digits

Address size

128 bits

Expansion rules

How IPv6 expansion works

  1. 1An IPv6 address always has eight 16-bit hexadecimal groups.
  2. 2Each visible group is left-padded with zeroes until it contains four digits.
  3. 3If :: appears, it is replaced with the number of 0000 groups needed to reach eight groups.

Binary representation

128 bits, grouped for inspection

Each block below represents one 16-bit IPv6 group. This form is useful when comparing prefix bits or troubleshooting subnet boundaries.

0000000000100001 0000110110111000 0000000000000000 0000000000000000 0000000000000000 0000000000000000 0000000000000010 0000000000000001
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