Regex Tester
Test regular expressions with live match highlighting
About Regex Tester
How Regex Tester Works
Evaluates regular expressions against sample text using ECMAScript RegExp engine with full flag support (g, i, m, s, u, y). Capture groups, match indices, and syntax highlighting calculate in real-time with zero telemetry, keeping proprietary test strings strictly local.
The Regex Tester helps you write and debug regular expressions with live match highlighting, capture group display, and flag controls. A typical use case is crafting a validation pattern for emails, phone numbers, or log lines and seeing matches update as you type. The tool shows which parts of your sample text matched and breaks out named and numbered groups, which makes complex patterns far easier to reason about. Everything runs in the browser, so your pattern and sample text never leave the page. It supports common flags like case-insensitivity and global matching, and surfaces errors immediately so you are not shipping broken expressions into production code.
Frequently asked questions
Which regex flavor is used?+
It uses the JavaScript RegExp engine available in your browser.
Does it save my patterns?+
No. Patterns and test text stay local and are not stored or uploaded.
Can I see capture groups?+
Yes. Matches and their groups are displayed separately for inspection.
Limitations
It follows JavaScript regex semantics, so some PCRE or other-engine features may behave differently.