Designed for developers who already know how to test regex but want to understand what someone else wrote. Or what they wrote three years ago and forgot.
Define test cases that should or shouldn't match. Useful for validating patterns before shipping.
Railroad diagram — read left to right. Quantifiers show as loops; alternation branches stack vertically.
Lead with what the pattern matches, then break it down token by token in a tree view. Other tools list tokens — we tell you the point.
Write a replacement with $1, $2, named groups, or $& and see the transformed text live. Test before you ship.
Define strings that should match and strings that shouldn't. Run them all in one click — like unit tests for your regex.
Get copy-paste-ready snippets for JavaScript, Python, Java, .NET, Go, Ruby, and PHP — with flavor-specific syntax handled automatically.
Walk through every position the engine probes, see where matches start and end, and understand exactly how your regex resolves.
Visualize complex patterns as left-to-right flowcharts with quantifier loops and alternation branches. Great for code reviews.
Measure performance on real input and run a growth test that detects catastrophic backtracking before it hits production.
Encode your pattern, flags, and test data in the URL fragment. Send a teammate a link — no account, no server, no tracking.
15 hand-tested patterns (email, URL, dates, UUID, semver, IPv4/v6, credit card, more) with dedicated explanation pages.
Describe what you want in plain English ("digits then a dash then four letters") and get a regex — useful for getting unstuck.
Port a regex between 7 flavors (JS, Python, Java, .NET, Go, Ruby, PCRE) with explicit warnings about features that don't carry over.
Build regex by clicking blocks instead of typing. Open the visual editor →
Everything runs client-side. Your patterns and test data never leave your device — unlike the major competitor.