| Match # | Matched Text | Position | Capture Groups |
|---|---|---|---|
| No matching strings found | |||
Our free JavaScript RegExp Tester & Matcher provides a real-time pattern testing environment to validate regular expressions, test pattern modifier flags (g, i, m, s, u), and extract matching strings in your browser. Features live HTML match highlighting, capture group extraction tables ($1, $2), and an integrated Regex search & replace mode. Select from pre-built expression templates (Email validation, URL extraction, IPv4 address finder, ISO date format) or test custom regular expressions against sample text payloads. Operating 100% in secure client-side JavaScript—your test data and regex rules are never uploaded to remote servers.
g, i, m, s, u)<mark> tag rendering$1/$2 sub-groupsregex-test.txt)Type your regular expression pattern and toggle pattern flags (g, i, m, s, u).
Paste your test text string or select a sample preset (Email, URL, IPv4, ISO Date).
Inspect highlighted matches, review captured groups in the table, and download regex-test.txt.
Evaluates standard JavaScript regular expressions with real-time syntax error validation and flag modifier support.
Breaks down regex match positions and displays captured parenthetical sub-groups ($1, $2) in a structured table.
All pattern matching, text highlighting, and search & replace operations execute locally in your browser. Text is never sent to external servers.
The ECMAScript Regular Expression Engine utilizes Nondeterministic Finite Automaton (NFA) evaluation to perform pattern matching, character class filtering, and string substitution.
Flag modifiers alter execution behavior: g (global search across full text), i (case-insensitive matching), m (multiline anchor matching for ^ and $), s (dotAll allows . to match newline characters), and u (unicode support).
Capture groups enclosed in parentheses (...) isolate extracted sub-patterns into indexed variables ($1, $2), enabling structured data parsing, log analysis, and replacement transformations.