Regex Tester
Test and debug regular expressions
Regular expressions describe repeating text structures in a compact language. Engineers rely on them for email and URL validation, resilient log parsing, and IDE-powered search and replace. Pare Dev mirrors ECMAScript flavor so you can rehearse production patterns safely. Matches refresh as you edit both the pattern and sample corpus, which exposes greedy pitfalls early.
Patterns combine character classes, quantifiers, capturing groups, non-capturing clusters, and anchors to bound matches. Flags include g for global scans, i for case folding, m for multiline caret behavior, s for dotall support in newer engines. Use this page before shipping form validators or crafting Splunk extraction rules. Document each capture group naming scheme so future maintainers understand intent. When catastrophic backtracking threatens performance, simplify alternations or possessive qualifiers after reproducing input here. Unicode property escapes require the u flag in modern browsers—flip it on when you need to block invisible bidirectional control characters in user handles. Lint rules from eslint-plugin-regex can diverge from runtime—validate the same string the server sees.
How to test regular expressions
- Enter pattern — Type your regex pattern in the pattern field.
- Enter test string — Paste or type text to test against. Matches highlight as you type.
- Adjust flags — Use g (global), i (case-insensitive), m (multiline) as needed.
FAQ
Is the regex tester free?
Yes. Free on this page, with limits noted per tool. All processing runs in your browser.
Does it work offline?
Yes. Once the page loads, testing works offline. No data is sent to any server.
Which regex flavors are supported?
JavaScript ECMAScript regex. Character classes, quantifiers, groups, anchors.
Can I test capture groups?
Yes. Parentheses create capture groups. Results show matched groups.
What are common flags?
g: global (all matches). i: case-insensitive. m: multiline (^ and $ per line).