Regex Tester - Live Match

Pasted a log line and got zero matches? When a valid pattern finds nothing, tap Check prefix: the app tries up to 32 shorter versions of your pattern on the same text and shows the longest prefix that does match and where — a clue, not a proof of the exact failing token. When it can't tell (alternation, lookaround, backreferences, several places), it says so. Then step through matches one tap at a time with context, UTF-16 ranges and numbered groups.

Test patterns on your device with Dart's ECMAScript regular-expression engine. See highlighted matches, positions and capture groups. Toggle ignore case, multiline and dot all; preview replacements with capture groups. Save named favorites with flags and recall recent successful patterns.

Code examples are available for JavaScript, Python, Dart, Java, Kotlin, Swift, Go, PHP and Ruby. Other engines may behave differently. This app does not execute or validate those engines. Copy is disabled for unsupported cross-engine syntax or flag combinations; verify examples in your target runtime.

Browse 45 reference patterns and 10 sample texts. Reference content includes Korean. Email, URL and similar patterns are learning examples, not security or complete input validation.

Matching runs in a cancellable background task with a 500 ms time limit. Limits: pattern 2,000 UTF-16 units, text/replacement 20,000 units, first 500 matches and 100,000 units of result data/output. Partial results are labelled; their total is unknown and replacement is unavailable. Simplify your input if a limit is reached.

Core matching, replacement, favorites and history work offline. No ads or tracking prompt. Share only when you tap Share; sharing uses your selected app. Copied text goes to your device clipboard. English controls; reference content includes Korean.