Regex Tester
Use this free Regex Tester to quickly get accurate results in seconds, free and instantly offline with no signup required ever, trusted by professionals in Austin, Chicago, Miami, Denver, Seattle, and New York for reliable daily use without accounts, subscriptions, limits, or delays on any device for everyday personal and business workflows daily.
Test regular expressions against text instantly in your browser with match highlighting and a flags menu. Free online regex tester — no data uploaded.
Calculator Inputs
About Regex Tester
Use this free Regex Tester to quickly get accurate results in seconds, free and instantly offline with no signup required ever, trusted by professionals in Austin, Chicago, Miami, Denver, Seattle, and New York for reliable daily use without accounts, subscriptions, limits, or delays on any device for everyday personal and business workflows daily.
Regex Tester: This free tool runs your JavaScript-flavored regular expression against a test string and reports every match with full details. Enter a pattern as /pattern/flags or a bare pattern, paste your test text, and get instant match results offline with no signup required ever.
Pattern Formats: The tool accepts both slash-delimited patterns with flags (like /\bfoo\b/gi) and bare patterns without slashes (like ^[a-z]+$). If you use the slash format, the flags g, i, m, s, u, y are all supported. The global flag is always added to find all occurrences.
Match Reporting: The tool shows the total match count and lists up to 50 individual matches. Each match is numbered for easy reference. When no matches are found, the tool confirms the pattern is valid but produced zero results — distinguishing between "no match" and "invalid pattern."
Error Handling: Invalid patterns produce a clear error message from the JavaScript regex engine. This includes details about the syntax error and often suggests what went wrong, making it easy to fix malformed patterns.
Flags Reference: g (global) finds all matches, i (case-insensitive) ignores case, m (multiline) treats ^ and $ as line boundaries, s (dotAll) lets . match newlines, u (unicode) enables full Unicode support, and y (sticky) matches only from the lastIndex position.
Browser-Based Privacy: All pattern matching happens in your browser using the native JavaScript RegExp engine. No data is sent anywhere, making this safe for testing patterns against sensitive content. The tool is completely free with no signup required ever.
Where it is used
A developer in Austin tests a email validation regex before deploying to a $1M SaaS platform. A Chicago data engineer validates a CSV parsing pattern. A Miami security researcher tests a password complexity regex. A Denver backend developer checks a URL routing pattern. A Seattle frontend engineer validates a phone number regex for a form. A New York fintech developer tests a currency matching pattern across transaction records.
How to use the Regex Tester
- Regular expression — enter the value (Slash-delimited pattern with optional flags, e.g. /foo/gi).
- Test string — enter the value (e.g. Paste the text to test against here…).
- Calculate — press the Calculate button to see the result instantly above.
Examples
Email pattern
Bare pattern
No match
Frequently Asked Questions
- Which regex flavour is this?
- JavaScript (ECMAScript) — the same engine used in browsers and Node.js. Lookaheads, backreferences, and Unicode properties are supported.
- Why does my pattern only show one match?
- Add the g (global) flag to the pattern — /foo/g — or the tester will show the first match only. The tool automatically adds g if missing.
- Is this tool free to use?
- Yes, this regex tester is completely free. Test unlimited patterns instantly offline with no signup required ever.
- Does it support lookahead and backreferences?
- Yes. The JavaScript regex engine supports positive and negative lookahead/lookbehind, backreferences, and named capture groups.
- What if my pattern has an error?
- The tool reports the exact error message from the JavaScript regex engine, including the error type and often a suggestion for what went wrong.
- Does it work offline?
- Yes. All pattern matching uses the native JavaScript RegExp engine in your browser with no network requests.