IP Address Format Converter - SimeonOnSecurity
NOTE: This tool runs entirely in your browser with client-side JavaScript. The address you enter is converted locally and is never transmitted, logged, or stored.
USE THIS ON SYSTEMS YOU OWN OR ARE AUTHORISED TO TEST. The alternate notations below exist to check whether your own input validation normalises an address before deciding to block it.
Equivalent Notations
| Enter an address to see its equivalent forms. |
Why Alternate Notations Matter
- A blocklist that matches strings, not values, is bypassable. A filter looking for
127.0.0.1misses2130706433, which is the same address. - Short forms are widely accepted. Many parsers read
127.1as127.0.0.1, and0as0.0.0.0. - The fix is normalisation, not more patterns. Parse the address into a 32-bit integer, then compare values. Pattern matching on the text always loses this race.
- IPv4-mapped IPv6 is the same trap.
::ffff:127.0.0.1reaches loopback and is routinely missed by IPv4-only checks.
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