Write your regular expression, set the flags, and paste your test text. Matches highlight in real time as you type, with a detailed breakdown of every match and its capture groups. No installation, no server round-trips — everything runs in your browser.
When to Use the Regex Tester
Use the regex tester when writing validation patterns, building search-and-replace rules, parsing log files, extracting data from text, or learning regular expressions with instant visual feedback.
Tips
- Start simple and build up. Test each part of your pattern before combining them.
- Use non-capturing groups (?:...) when you need grouping but do not need the captured value — it is slightly faster.
- The multiline (m) flag is essential when you want ^ and $ to match at line boundaries, not just the start and end of the entire string.
- If your pattern runs slowly, look for nested quantifiers like (a+)+ which cause catastrophic backtracking.