Type a regular expression and some test text, and the tester lists every match with its start index, length and capture groups. For example, [A-Z] run against 'The quick brown fox jumps over the lazy dog. It barked.' finds 2 matches, T at index 0 and I at index 45. Syntax errors are reported as you type.
Writing a pattern for form validation, log parsing or a search-and-replace usually takes a few tries, and running the whole program after each edit is slow. This tester compiles your expression with the browser's own JavaScript RegExp engine, so what you see is what JavaScript and Node.js will do. Each match is listed in a table with its position, length and the text captured by each group, and the compiled form with its flags is shown so you can paste it straight into code. The global flag is always on, so every match is found, not just the first. One limit: other engines such as PCRE, Python re or .NET support features JavaScript lacks, like possessive quantifiers, so a pattern that passes here can still differ elsewhere.
Type the regular expression without slashes, for example \d{3}-\d{4}.
Turn on i, m, s or u as needed; the global flag is applied automatically.
Paste the text to search, or open a .txt, .csv or .log file from your device.
Check the table for each match, its index, length and capture groups.
Result Matches: 2
Compiled as: /[A-Z]/g
Capture groups: 0
Characters matched: 2
Text length: 55
The class [A-Z] finds the two capitals, T at index 0 and I at index 45.
Result Matches: 2
Compiled as: /(\d{4})-(\d{2})-(\d{2})/g
Capture groups: 3
Characters matched: 20
Text length: 40
Each date matches as a whole and the three groups split out year, month and day.
Result Matches: 4
Compiled as: /cat/gi
Capture groups: 0
Characters matched: 12
Text length: 30
With the i flag, cat matches Cat, CAT, cat and the cat inside concatenate.
matches = every result of RegExp(pattern, 'g' + flags).exec(text), advancing past empty matches
patternflagsindexThe pattern is compiled with the global flag plus the flags you choose. exec() is called repeatedly; each call returns the next match and its groups. When a match is empty, the search position moves forward one character so the loop cannot stall. The first 200 matches are listed; the count covers all of them.
ECMAScript, the engine built into your browser. Results match what JavaScript in a browser or Node.js returns, including lookbehind and named groups in current browsers.
The global flag is always applied so the table can list every match. Without it, exec() would stop at the first match and the count would never exceed one.
Patterns such as a* or \b can match zero characters. The tester records the position and moves on by one character, and a warning tells you the pattern can match nothing.
Each group is listed by number with the text it captured, separated by a bar. A group that did not take part in the match shows (no match), which is common with alternation.
The engine could not compile it, usually because of an unclosed bracket or parenthesis, a quantifier with nothing before it, or an invalid escape in u mode. The engine's own message is shown under the field.
No. The pattern is compiled and run in your browser, and neither the pattern nor the text leaves your device or is stored.
Using this tool in an assignment, article or report? Copy a citation, or a link for your website.
Tools Directory Editorial Team. (2026, October 23). Regex Tester. Tools Directory. Retrieved October 26, 2026, from https://tools.milunir.com/developer-tools/developer-reference/regex-tester/
Tools Directory Editorial Team. “Regex Tester.” Tools Directory, 23 Oct. 2026, https://tools.milunir.com/developer-tools/developer-reference/regex-tester/. Accessed 26 Oct. 2026.
Tools Directory Editorial Team. “Regex Tester.” Tools Directory. Last modified October 23, 2026. Accessed October 26, 2026. https://tools.milunir.com/developer-tools/developer-reference/regex-tester/.
<a href="https://tools.milunir.com/developer-tools/developer-reference/regex-tester/">Regex Tester – Tools Directory</a>