Free Online Regex Tester
Test regular expressions in real time with live match highlighting, and let AI explain any regex in plain English.
Learn character classes, quantifiers, groups, and when regex is overkill vs. the right tool.
to generate and explain regex with AI. Included in the Free plan.
Quick reference
.Any character\dDigit [0-9]\wWord char [a-zA-Z0-9_]\sWhitespace^Start of string$End of string*0 or more+1 or more?0 or 1 (optional){n,m}Between n and m[abc]Character class[^abc]Negated class(abc)Capture group(?:abc)Non-capture groupa|bAlternation (a or b)\bWord boundaryAbout this tool
Regex Tester
A regex tester lets you write a regular expression and see exactly what it matches in a sample string, in real time. Type a pattern, paste your test text, and every match is highlighted instantly so you can fine-tune the expression without guesswork.
This tool also explains any regex in plain English using AI, so you can understand an unfamiliar pattern, debug a tricky capture group, or learn how lookaheads and character classes work as you go. It runs entirely in your browser and is free on the HACKUP Free plan.
Frequently asked questions
Regex Tester FAQ
- What is a regex tester?
- A regex tester is a tool that runs a regular expression against sample text and highlights the matches as you type, so you can verify and refine your pattern before using it in code.
- Is this regex tester free?
- Yes. The regex tester, including live matching and AI explanations, is included in the HACKUP Free plan with no account required to try it.
- Which regex flavor does it use?
- It uses the JavaScript (ECMAScript) regular expression engine, the same one that runs in browsers and Node.js. Flags like g (global), i (case-insensitive), and m (multiline) are supported.
- Can it explain what a regex does?
- Yes. The built-in AI explainer breaks any pattern down into plain English, describing each token, group, and quantifier so you can understand or learn from it.