Regex Tester — Free Online Tool
Write and test regular expressions against sample text with real-time match highlighting directly in the input. See all matches, capture groups, and named captures listed clearly below. Supports all JavaScript RegExp flags (g, i, m, s, u). Ideal for developers building validation rules, parsers, or search patterns.
100% client-side. No uploads. Your data never leaves your browser.
How to use Regex Tester
- Enter your regular expression in the pattern field (without surrounding slashes).
- Select any flags (g, i, m, s, u) using the flag toggles.
- Type or paste test text in the input area — matches highlight in real time.
- Review all matches and capture groups in the results panel below.
Frequently Asked Questions
Which regex flavor does this use?
JavaScript's built-in RegExp engine. This is compatible with most modern regex flavors but may differ from PCRE (PHP, Python) in some edge cases.
How do I use named capture groups?
Use the syntax (?<name>pattern). Named captures appear in the results panel labelled with their group name.
Can I test multiline strings?
Yes. Paste multiline text and use the 'm' flag to make ^ and $ match start/end of each line rather than the whole string.
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