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Test and debug JavaScript ECMAScript regular expressions with real-time match highlighting, group capture display, and flag toggles (g, i, m, s, u).
Follow these simple steps to get instant, accurate results directly in your browser:
Type your regex pattern (e.g. ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$) into the pattern bar.
Enable or disable flags: g (global), i (ignore case), m (multiline), and s (dotAll).
Paste your test string and view highlighted match spans and captured group details.
The Regex Tester is a real-time Regular Expression testing and debugging environment that highlights pattern matches, captures groups, and validates JavaScript RegExp syntax instantly.
It supports standard JavaScript RegExp flags (global g, case-insensitive i, multiline m, dotAll s, and unicode u). As you type your pattern, the engine parses match intervals, evaluates capturing groups ($1, $2, named groups), and highlights matching text in the test string with distinct background colors.
Because regular expressions are frequently used to sanitize private logs and proprietary datasets, the regex engine runs 100% client-side with zero data transmission.
Instantly highlights matches and capture groups as you construct patterns.
Easily configure global, multiline, case-insensitive, and unicode flags.
Breaks down numbered and named capture groups with character index positions.
Your test strings and regex patterns never leave your machine.
Design and verify regex patterns for emails, phone numbers, postal codes, and passwords.
Extract specific IP addresses, timestamps, and error codes from server log dumps.
Test complex substitution expressions before applying them across source code files.
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