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In free text (logs, articles, dumps) it's common to want to extract URLs and IP addresses. Let's look at robust patterns for both.

http/https URLs

Pattern: https?:\/\/[\w.-]+(?:\:\d+)?(?:\/[^\s]*)?

• https?:\/\/ -- scheme, with the s optional.
• [\w.-]+ -- host (domain, subdomains, possibly localhost).
• (?:\:\d+)? -- optional port.
• (?:\/[^\s]*)? -- optional path, up to the first whitespace.

Captures https://example.com, http://localhost:3000/api/users, https://docs.dev/path?query=value.

IPv4

An IPv4 is 4 decimal octets separated by dots:

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

"Good enough" version: it also accepts invalid values like 999.999.999.999. For the strict version you'd need range alternation (25[0-5]|2[0-4]\d|[01]?\d\d?), which is much longer.

Pattern (strict): \b(?:(?:25[0-5]|2[0-4]\d|[01]?\d\d?)\.){3}(?:25[0-5]|2[0-4]\d|[01]?\d\d?)\b

Precision versus brevity

Matching URLs or IPs requires balancing pattern tolerance. A strict IP validator verifies that no octet exceeds 255. A practical extractor, on the other hand, typically looks for simplified patterns and delegates fine validation to dedicated code.

Try it

Review exercise

Additional challenge