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Regex Explainer

Explain any regular expression in plain English

Plain English
Token-by-token
    Want to test your regex against real text? → Regex Tester
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    Learn more — how it works, FAQ & guide
    Click to expand

    Free regex explainer — plain English breakdown of any pattern

    Toololis Regex Explainer translates any regular expression into plain English. Paste a cryptic pattern, see what each token does. Perfect for reviewing legacy code, learning regex, or documenting complex patterns.

    How to use this tool

    1. 1

      Paste your regex

      Any JavaScript-style regex pattern. No leading/trailing slashes needed.

    2. 2

      Read the explanation

      Each token gets a plain-English description. Character classes, anchors, quantifiers, groups — all explained.

    3. 3

      Try presets

      Common patterns (email, URL, phone) come pre-loaded. See how they work.

    What we explain

    • Character classes — [a-z], [0-9], [^abc]
    • Anchors — ^, $, \b, \B
    • Quantifiers — *, +, ?, {n}, {n,m}, lazy (*?)
    • Groups — (), (?:), (?<name>), alternation |
    • Lookarounds — (?=), (?!), (?<=), (?<!)
    • Shortcuts — \d, \w, \s, \D, \W, \S
    • Escapes — \., \\, \n, \t

    Frequently Asked Questions

    What regex flavor is supported?
    JavaScript regex (ECMAScript). Covers 95% of regex you'll see. Some PCRE-only features (like atomic groups) aren't valid in JS but we flag them.
    Is this 100% accurate?
    Very close — we parse the regex token-by-token using a real regex-to-AST approach. Complex lookbehind / recursive patterns may have simplified explanations.
    Does it show what the regex matches?
    For explanation, yes. For testing matches against text, use our Regex Tester.
    Why do I need this?
    Regex is famously "write-only" — easy to write, hard to read. When you come back to old code or inherit someone else's regex, this saves minutes of decoding.
    What about regex I don't fully understand?
    Paste it here — you'll see what each piece does. Great for learning regex without reading a textbook.

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