Free Regex Tester
Test JavaScript regular expressions live. Match highlighting, capture groups, all flags, and a quick-pick library of common patterns. Pairs with the regex cheatsheet for reference.
AI regex helperFree
Describe what you want to match — AI writes the regex + test examples.
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Frequently asked questions
What is a regex tester used for?
A regex tester lets you write and immediately verify regular expression patterns against sample text. You see matches highlighted, capture groups extracted, and any syntax errors flagged — no need to run code locally or set up a script.
Does this regex tester support flags like /g and /i?
Yes. Toggle any combination of g (global), i (case-insensitive), m (multiline), s (dotall), u (unicode), and y (sticky). Output and code snippets update live as you change flags.
Can it generate code snippets for my language?
Yes — paste a working pattern and instantly see equivalent code for JavaScript, Python, PHP, and Java. AI mode also explains what each token in the regex actually does.
Is my data sent to a server?
Regex matching runs entirely in your browser. The optional AI explain / build features send only the pattern (or your English description) to the AI API — never your test data.
Can AI write a regex from plain English?
Yes. Switch to the AI tab, describe what you want to match (e.g. 'US phone number with optional country code'), and the AI returns a working regex plus example inputs that match and don't match.
Regex testers usually require you to write the pattern first. Ours adds an AI builder — describe what you want to match in plain English and AI writes the regex, plus a built-in cheat sheet, code snippets for JS / Python / PHP / Java, and live match highlighting.
How to use
- 1Switch to the 'AI regex helper' tab.
- 2Type plain English — e.g. 'match a US phone number with optional country code'.
- 3Click 'Build regex' — AI returns the pattern + test inputs that match and don't.
- 4Or paste your existing regex, click 'Explain my regex' — AI breaks down every token.
- 5Test against your own text in the main tab — matches highlight live.
Why use this tool
- AI English-to-regex eliminates the hardest part of regex.
- Built-in cheat sheet of all 30 common patterns.
- Code snippets in 4 languages — no manual translation.
- Catastrophic backtracking warning prevents ReDoS bugs.
Real-world examples
Form validation
Describe 'email like name@domain.com but allow + and . in name' → AI generates the regex + tests it on 'ada.lovelace+work@toolify.dev' (match) vs 'ada@invalid' (no match).
Learning regex
Paste a complex regex like (?<=foo)bar(?!baz) → AI explains lookbehind, lookahead, and the full intent.
Code generation
Working pattern shown → see equivalent JavaScript, Python, PHP, and Java code instantly. Copy and paste into your file.