- Is this regex explainer free?
- Yes, DevFlow Regex Explainer is completely free with no usage limits. All parsing, explanation, and Markdown export runs directly in your browser — no account required.
- Is my data safe?
- All regex parsing and explanation happens entirely in your browser using JavaScript. No patterns, explanations, or Markdown exports are ever transmitted to a server or stored anywhere outside your browser. Your data stays completely private on your machine.
- What types of regex tokens does it explain?
- The explainer covers all major regex constructs: character classes (\d, \w, [a-z]), quantifiers (*, +, ?, {n,m}), groups ((...), (?:...), (?<name>...)), anchors (^, $, \b), lookaheads/lookbehinds ((?=...), (?!...), (?<=...), (?<!...)), alternations (|), backreferences (\1, \k<name>), Unicode properties (\p{Letter}), and escapes.
- What are lookahead and lookbehind assertions?
- Lookaround assertions check for a pattern without including it in the match. (?=...) is a positive lookahead (match only if followed by ...), (?!...) is a negative lookahead (match only if NOT followed by ...), (?<=...) is a positive lookbehind (match only if preceded by ...), and (?<!...) is a negative lookbehind (match only if NOT preceded by ...). They are zero-width — they do not consume characters.
- What are named capture groups?
- Named capture groups use the syntax (?<name>...) to assign a name to a capture group instead of just a number. For example, (?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2}) captures year, month, and day as named groups. Named groups make regex more readable and maintainable, especially when working with complex patterns.
- What are backreferences in regex?
- Backreferences allow you to match the same text that was captured earlier in the regex. For example, (\w+)\s+\1 matches a word followed by whitespace, then the same word again. You can reference numbered groups with \1, \2, etc., or named groups with \k<name>. Backreferences are useful for matching repeated patterns like duplicate words or balanced tags.
- What is the difference between greedy and lazy quantifiers?
- Greedy quantifiers (*, +, ?, {n,m}) match as much text as possible by default. Lazy quantifiers (*?, +?, ??, {n,m}?) match as little text as possible. For example, .* matches the entire string 'abc123def', while .*? matches just 'a' (the first character). Use lazy quantifiers when you want to match the shortest possible substring — common with HTML/XML parsing and delimited data.
- What regex flags are supported?
- The tool supports 8 JavaScript regex flags: g (global — find all matches), i (case-insensitive), m (multiline — ^ and $ match line boundaries), s (dotall — . matches newlines), u (unicode — handle surrogate pairs), v (unicodeSets — ES2024 set operations), d (indices — include match indices), and y (sticky — match at exact position only).
- How is complexity scored?
- Complexity is scored from 1 to 10 based on the regex structure: count of nested groups, number of quantifiers, presence of lookarounds, alternations, and backreferences. A score of 1–3 is Simple, 4–6 is Moderate, 7–8 is Complex, and 9–10 is Very Complex. The badge helps you gauge pattern maintainability at a glance.
- Can I explain regex with the `u` (Unicode) flag?
- Yes. The explainer fully supports the u flag, which enables proper Unicode handling. With this flag, \p{Letter}, \p{Script=Greek}, and other Unicode property escapes work correctly. The parser also handles surrogate pairs and astral characters properly when the u flag is set.
- What is the difference between the Regex Explainer and Regex Tester?
- The Regex Explainer focuses on understanding regex patterns — it breaks down any regex into plain English, visualizes token structure, and generates Markdown documentation. The Regex Tester focuses on validating regex against test strings — it highlights matches, shows capture groups, supports replace/split modes, and generates code snippets. Use the Explainer to learn or document regex; use the Tester to debug and test regex.
- Does it work offline?
- Yes. All regex parsing, explanation, and Markdown export is done using JavaScript. Once the page has loaded, the Regex Explainer works without an internet connection.
