Regex Tester
Test regular expressions and highlight matches in real time.
Regex Explain
Break down a regex pattern into color-coded tokens with plain-language explanations for each part.
Input data is processed in your browser
Data is never sent to a server
Tool
What is Regex Explain?
Regex Explain breaks a regular expression down into its individual tokens, color-codes each one by type, and provides a plain-language description of what each part does.
Hover over any token in the colorized view to highlight its corresponding explanation. Built-in examples for email, date, URL, IPv4, and hex color patterns let you explore real-world regular expressions instantly.
How to Use
- Enter a regex pattern in the input field (no slashes needed).
- Toggle flags (g, i, m, s) with the flag buttons.
- The colorized view shows each token highlighted by type.
- The explanation list describes what each token does.
- Optionally enter a test string to see match highlights.
FAQ
Which regex components are recognized?
Anchors (^ $ \b \B), quantifiers (* + ? {n,m} and their lazy variants), capture groups (named, non-capturing, lookahead, lookbehind), character classes ([...]), escape sequences (\d \w \s etc.), the dot metacharacter, alternation (|), and literal characters.
How are greedy vs lazy quantifiers shown?
Quantifiers followed by ? are described as lazy (shortest match), while those without ? are described as greedy (longest match).
Can it handle nested groups?
Yes. The tokenizer processes the pattern left-to-right, so nested groups are each tokenized and explained individually. Structural validity is checked by the JavaScript RegExp engine.
Is my data sent to a server?
No. All processing happens entirely in your browser.
More Tools in This Category
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- Regex Replace TesterTest regex search and replace in real time with match highlights and capture group details.
- Regex EscapeAutomatically escape regex metacharacters in a string for safe use in patterns.
- Regex Cheat SheetA searchable quick reference for regex syntax — click any card to copy.