Regex tester & visual builder

Build a JavaScript regex by selecting parts of a sample line. Test multiline logs, highlight matches and navigate results. Free browser tool with worker processing.

Enable JavaScript to use this interactive tool. Paste input, choose options, then copy or download the result, or save it to your notebook.

Details and limits

Build a JavaScript regex from a sample log line, then match the original text. Choose suggested fields, capture groups, or edit the pattern directly. Processing runs in a worker; matching stops after 1.5 seconds. Results and previews are bounded.

Example and common questions

Capture an order number

Regex pattern: order=(\d+)
Regex flags: g
Maximum matches: 100

Input

order=42

First match — excerpt

{
  "from": 0,
  "to": 8,
  "match": "order=42",
  "groups": [
    "42"
  ],
  "namedGroups": null
}

Which regex syntax is supported?

The tester uses JavaScript regular expressions and supported JavaScript flags. Syntax from other regex engines may need changes.

What do positions and groups mean?

Groups contain captured text. Positions are UTF-16 offsets into the original input, with an inclusive start and exclusive end.

Why can results stop early?

Match and result budgets bound the output, and processing has a worker timeout. See Details and limits. Simplify a pattern or reduce the input when processing stops.

Common errors and limitations

Check invalid patterns, unsupported or duplicate flags, and timeouts. Your input remains available for correction; a timeout does not mean the pattern has no matches.