Developer Tools
Regex Tester
Test JavaScript regex patterns live. See matches, capture groups, position. All flags supported.
//
7 matches
- @0Hello
- @6world
- @13regex
- @19testing
- @271
- @292
- @313
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Your files never leave your device. No upload, no servers.
About Regex Tester
Regex Tester runs JavaScript regular expressions against your test string in real time. Toggle the standard flags (g, i, m, s, u, y), view every match with its position, and inspect capture groups individually.
Useful for prototyping a pattern before pasting into code, debugging why a regex isn't matching what you expected, and learning how flags change behavior. Runs in your browser — no upload, no telemetry.
The tester uses your browser's native RegExp engine, which is the same engine that runs your production JavaScript and Node.js code. Patterns that work here behave identically when you ship them, with no flavor mismatches between PCRE, Python re, and JavaScript regex (a common gotcha when prototyping in tools that use a different engine). Match positions are reported as start/end character indices, capture groups are listed by index and by name (for named groups), and the matched text in the test string is highlighted live as you edit either side.
How Regex Tester works
- Type or paste a regex pattern in the pattern field. The literal slashes are optional — type 'foo' or '/foo/g'.
- Pick the flags you want: g (global), i (case-insensitive), m (multiline ^/$), s (dot-all), u (unicode), y (sticky).
- Paste your test string into the input area. Matches highlight in real time as you type.
- View each match with its start position, length, and any capture groups (numbered and named).
- Iterate on the pattern until matches look right, then copy the regex literal into your code.
When to use Regex Tester
- Prototype an email-validation regex before adding it to your form-validation logic.
- Debug why a regex isn't matching the strings you expect — see character-by-character what's happening.
- Test that a URL/path/route pattern matches every variation it should, and rejects what it shouldn't.
- Learn how flags change behavior (e.g. multiline ^/$ behavior, dot-all matching newlines).
- Build a pattern for log parsing by iterating against real log lines.
- Verify a search-and-replace regex before running it across a large codebase.
Why choose Utilix Regex Tester
- Uses the actual JavaScript RegExp engine — no flavor mismatch when you ship to production.
- Lists matches with positions and named groups, not just a yes/no.
- All evaluation is local — safe for testing patterns against confidential log data or PII.
- No paywall, no popups, no ads. Regex101 makes you sign in to save patterns; here patterns persist locally.
- Live highlighting helps you spot why a near-miss isn't matching.