IPv4 Header Decoder

Paste raw IPv4 header hex and decode every field: addresses, TTL, protocol, flags, and more.

IPv4 header hex (≥ 20 bytes)

Invalid hex. Use hex digits, spaces/colons/0x separators allowed.

How to read the result

The first byte holds version (must be 4) and header length. Bytes 12–19 are source and destination addresses; byte 8 is TTL; byte 9 is the protocol number.

Example

4500003c... → version 4, src 10.0.0.1, dst 10.0.0.2, proto TCP

FAQ

How many bytes do I need?

At least 20 bytes (40 hex chars). Longer headers include IP options.

Why 'version != 4' error?

The top nibble of byte 0 must be 4 — other values are IPv6 or garbage.