regex match IPv4 address
Quick Answer
# Match any IPv4-shaped string (fast, simple)
/\b\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\b/
# Strict — enforces 0-255 per octet
/\b(?:(?:25[0-5]|2[0-4]\d|1\d{2}|[1-9]\d|\d)\.){3}(?:25[0-5]|2[0-4]\d|1\d{2}|[1-9]\d|\d)\b/Usage
Extract IP addresses from logs or validate that a string is a valid IPv4 address.
Other causes & fixes
Strict octet range breakdown
25[0-5] 250-255
2[0-4]\d 200-249
1\d{2} 100-199
[1-9]\d 10-99
\d 0-9JavaScript — extract IPs from log
const log = 'Connection from 192.168.1.1 and 10.0.0.255';
const ipPattern = /\b(?:(?:25[0-5]|2[0-4]\d|1\d{2}|[1-9]\d|\d)\.){3}(?:25[0-5]|2[0-4]\d|1\d{2}|[1-9]\d|\d)\b/g;
log.match(ipPattern)
// ['192.168.1.1', '10.0.0.255']Python — use ipaddress module for validation
For validation, the standard library is more reliable than regex.
import ipaddress
def is_valid_ipv4(addr):
try:
ipaddress.IPv4Address(addr)
return True
except ValueError:
return False
is_valid_ipv4('192.168.1.1') # True
is_valid_ipv4('999.0.0.1') # FalseRelated