~/regex-tester

Match IPv4 addresses with regex

A loose IPv4 pattern that catches dotted-quads and a strict variant that rejects 999.999.999.999. Pick the one that matches your validation budget.

# pattern

/\b(?:\d{1,3}\.){3}\d{1,3}\b/g

→ Open in regex tester (pre-filled)

# how it works

Three groups of one-to-three digits followed by dots, then one final group. Word boundaries (`\b`) prevent matching inside longer strings. This is the *loose* form — it accepts 999.999.999.999.

# sample input

router 192.168.1.1 dns 8.8.8.8 garbage 999.999.999.999 internal 10.0.0.1

# pitfalls

• The strict form bounding each octet to 0-255 is much longer: (25[0-5]|2[0-4]\d|[01]?\d?\d) repeated 4× with dots. Only worth it when the input is hostile.
• Does not validate that the address is routable, private, or actually assigned. That is a network question, not a regex one.
• IPv6 is a different grammar entirely. Don't try to merge them into one pattern.

# other patterns

• Match email addresses with regex
• Match URLs with regex
• Match UUIDs with regex
• Match ISO 8601 dates with regex
• Match hex color codes with regex

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