What regex flavor does this use?

JavaScript's built-in RegExp engine (ECMAScript regex syntax) — the same flavor used in browser JS and Node.js. Some features from other flavors like PCRE (e.g. certain lookbehind or recursive patterns) may behave slightly differently or be unsupported.

Why do I only see non-overlapping matches?

The tester runs the pattern with the global flag to find every match, and by default a regex engine advances past each match before searching for the next — so overlapping matches (e.g. searching for 'aa' in 'aaa') aren't both reported unless you use a lookahead trick.

Regex Tester

Test regular expressions against sample text and see all matches.

How this is calculated

Runs new RegExp(pattern, flags) against the test string and collects all matches

Assumptions used in this calculation

Regex engine: Patterns are evaluated using JavaScript's native RegExp (ECMAScript syntax), with the global flag applied automatically to find all matches.

About this calculator

The regex tester runs a JavaScript regular expression against a test string and lists every match with its position.

Worked example

\d+ against 'abc 123 def 456'

Result: 2 matches: 123, 456

Was this helpful?

Frequently asked questions

JSON Formatter & Validator

Format, validate and minify JSON data.

Regex Tester

About this calculator

Frequently asked questions

What regex flavor does this use?

Why do I only see non-overlapping matches?

Related calculators