Regex Pattern Library

17 ready-made patterns, each one explained part by part, tested against match and no-match examples, and copy-pasteable into JavaScript, Python, SQL, GA4 and BigQuery. Click any Try link to load the pattern straight into the tester with sample data.

Dates & Time

• Regex to Match Dates in YYYY-MM-DD Format — Full-match an ISO-style calendar date with day/month ranges that actually hold.
• Regex to Match an ISO 8601 DateTime — Match 2026-10-28T14:30:00Z and friends, with or without offset and milliseconds.
• Regex to Match Time in HH:MM (or HH:MM:SS) Format — Range-limited 24-hour clock match, seconds optional.

Validation

• Practical Email Validation Regex — The sane email pattern: what it catches, what it deliberately skips.
• UUID Regex (8-4-4-4-12) — Match 550e8400-e29b-41d4-a716-446655440000 anywhere or full-line.
• IPv4 Address Regex (Octets Limited to 0–255) — The classic dotted-quad pattern, minus the 999 octet bug.
• Hex Color Regex (#RGB and #RRGGBB) — Match 3- or 6-digit hex colors with or without the hash.
• SemVer 2.0.0 Regex — Strict core + optional pre-release + optional build metadata.
• URL Slug Regex (lowercase-with-hyphens) — Validate seo-friendly slugs: no spaces, no double hyphens, no uppercase.

Extract & Replace

• Regex to Extract Numbers from a String — Find integers, decimals and signed values inside any text.
• Regex to Extract the Domain from a URL — One capture group: pull example.com out of any full URL.
• File Extension Regex — Match the extension at the end of a path — or the whole filename.
• Regex to Match Quoted Strings — Match "..." or '...' without leaking past the closing quote.

URLs & Marketing

• Practical URL Regex (http / https) — Match real web links in text — readable, RE2-safe, honest limits.
• Regex to Remove Query Parameters from a URL — Strip everything from ? onward (or only utm_* params) cleanly.
• UTM Parameter Regex (match & extract utm_*) — Find, extract or validate the five utm_* parameters in any URL.

Dev & Logs

• Log Level Regex (DEBUG / INFO / WARN / ERROR / FATAL) — Pull the level out of a log line, or filter whole lines by severity.

GA4 guides

• GA4 regex cheat sheet — 25+ copy-paste patterns for segments, audiences and filters.
• GA4 page path regex guide — filter page_location with full-match semantics.
• GA4 event filter regex guide — pick event names precisely.
• GA4 regex match types — full match vs partially matches, per GA4 surface.
• Custom channel grouping regex guide — build reliable channel rules.
• RE2 vs PCRE — why patterns that work in JavaScript can fail in GA4 and BigQuery.

Every pattern on this page is RE2-compatible unless its page says otherwise — meaning it also works in Google Analytics 4, BigQuery, Go and Rust. Regex matching in the tester uses your browser's native engine; check the RE2 vs PCRE differences before shipping patterns to Google tools.