Why is 010.0.0.1 rejected?

Because it is ambiguous. Traditional C parsers read a leading zero as octal, making `010` the number 8, while most modern libraries read it as decimal 10. Attackers use that gap to make a validator and the eventual connection disagree about the destination. The tool rejects it rather than guessing an interpretation for you.

What are the IPv6 compression rules?

RFC 5952: always lowercase, strip leading zeros from each group, and collapse the **longest** run of zero groups with `::`, only once per address. On a tie, the earliest run wins. Following the same rules means the output matches what most systems produce when they normalise an address.

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IP Address Format Converter

Convert IPv4 between dotted decimal, integer, hexadecimal, and binary, and expand or compress IPv6.

Input

IP address

IPv4 formats

Dotted decimal192.168.1.10

Decimal integer3,232,235,786

Hexadecimal0xC0A8010A

Binary11000000.10101000.00000001.00001010

Octal0300.0250.01.012

IPv4-mapped IPv6::ffff:192.168.1.10

Reverse DNS10.1.168.192.in-addr.arpa

About this tool

Enter an IPv4 address to get the decimal integer, hexadecimal, binary, octal, IPv4-mapped IPv6, and reverse DNS name at once. Enter an IPv6 address to get the fully expanded form, the RFC 5952 compressed form, the ip6.arpa reverse name, and the embedded IPv4 if it is a mapped address. Addresses like `010.0.0.1` are rejected: some parsers read the leading zero as octal and others as decimal, and that disagreement is exactly how address validation gets bypassed.

How it works

Enter an IPv4 or IPv6 address.
Read every equivalent representation.
Copy whichever format you need.

Limits and notes

IPv4 octets with a leading zero are rejected, because parsers disagree on their meaning and that disagreement is a common validation bypass.

Privacy

Addresses and strings are calculated inside this browser only. Nothing is uploaded, stored, or written to the URL or any log.

Frequently asked questions

Why is 010.0.0.1 rejected?: Because it is ambiguous. Traditional C parsers read a leading zero as octal, making `010` the number 8, while most modern libraries read it as decimal 10. Attackers use that gap to make a validator and the eventual connection disagree about the destination. The tool rejects it rather than guessing an interpretation for you.
What are the IPv6 compression rules?: RFC 5952: always lowercase, strip leading zeros from each group, and collapse the **longest** run of zero groups with `::`, only once per address. On a tie, the earliest run wins. Following the same rules means the output matches what most systems produce when they normalise an address.

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