● Developer Utilities
Regex Tester
Test regular expressions with match indices, flags, and capture groups in a Web Worker.
Processed locally. Your input stays in this browser.
Zero Data SentWeb Worker Isolated Execution Active (300ms Hard Timeout)Zero Main-Thread Freeze
//g
Flags:
Matches Found: 0
Worker Execution Time: 0 ms
1 line•69 chars•69 B
Ctrl/Cmd+Enter run
Matched Groups (0)
No matches found for the given expression and test string.
What Regex Tester Does
Test JavaScript Regular Expressions with real-time match highlighting, match count, and group extraction.
How It Works
- 1.Enter your Regular Expression pattern (without enclosing slashes).
- 2.Toggle flags (g: global, i: ignore case, m: multiline, s: dotAll, u: unicode).
- 3.Paste your test string. Regex runs in an isolated Web Worker with a 300ms termination guard.
Common Use Cases
- •Testing email, phone, or URL validation expressions safely.
- •Debugging search & replace expressions without freezing your browser on pathological patterns.
Related Developer Guides
Cron Expression Examples & 5-Field Reference Guide
Complete cron expression reference guide with 20+ copy-paste examples. Learn standard 5-field Unix crontab syntax, special characters (*, /, -, ,), and timezone handling.
Read GuideRegex Testing & Optimization Guide for Developers
Comprehensive guide to testing regular expressions in JavaScript. Learn character classes, flags (g, i, m, s, u), capture groups, lookaheads, and how to avoid catastrophic backtracking.
Read GuideFrequently Asked Questions
Does this tester safeguard against catastrophic backtracking?
Yes. An isolated Web Worker with a 300ms termination timeout prevents browser freezing.