Networkingflags: g

Private IP Address (RFC 1918)

Match IPv4 addresses in the RFC 1918 private ranges: 10/8, 192.168/16, and 172.16/12.

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Available in

JSSupported

JavaScript / ECMAScript

Browser-native RegExp. Default if you don't pick.

PYSupported

Python (re)

CPython stdlib `re`. Unicode-aware `\w` and `\d` by default.

GOSupported

Go (RE2)

Linear-time matching. No backreferences or lookarounds.

Pattern

regexengine-agnostic

\b(?:10(?:\.\d{1,3}){3}|192\.168(?:\.\d{1,3}){2}|172\.(?:1[6-9]|2\d|3[01])(?:\.\d{1,3}){2})\b   (flags: g)

Raw source: \b(?:10(?:\.\d{1,3}){3}|192\.168(?:\.\d{1,3}){2}|172\.(?:1[6-9]|2\d|3[01])(?:\.\d{1,3}){2})\b

How it works

Three top-level alternatives cover the three reserved private ranges. 10(?:\.\d{1,3}){3} matches 10.x.x.x. 192\.168(?:\.\d{1,3}){2} matches 192.168.x.x. 172\.(?:1[6-9]|2\d|3[01]) constrains the second octet to the 16–31 sub-range, then (?:\.\d{1,3}){2} matches the last two octets. \b boundaries prevent partial-IP matches inside longer numbers.