RegExplain
Plain-English regex explanations and a live tester. JavaScript RegExp, Python re, or PCRE-oriented notes. Nothing leaves your browser.
We’re improving this tool based on real use—try it and tell us what would help you most.
Standard `RegExp` for explanation and preview.
Plain-English explanation
Flavor: JavaScript RegExp
Flags: g (find all matches)
Match digit character (0–9), repeated exactly 3 times. Then Match the character "-". Then Match digit character (0–9), repeated exactly 4 times.
Practical examples
Each link opens the same tool with a realistic starter pattern and sample text. Edit freely—use them as templates, not as production validators.
How it works
RegExplain parses your pattern with the same grammar as JavaScript RegExp (using regexpp), walks the syntax tree, and turns each part into a short plain-English phrase—quantifiers, groups, character classes, assertions, and escapes.
The test string runs in your browser with RegExp: matches are highlighted. Choose a flavor (JavaScript, Python re, or PCRE notes): JavaScript uses native semantics end-to-end; Python and PCRE add flag labels and notes where those engines can differ, while the live preview still uses mapped JavaScript flags.
Share links store pattern, flags, flavor, and sample text in the URL hash—nothing is sent to a server.
Limitations
Not validation advice. Example patterns are educational shortcuts. Real apps need allowlists, libraries, or context-specific rules.
Dialect differences. Python and PCRE modes describe common flags and caveats, but parsing follows JavaScript rules.
URLs and privacy. Shared links can get long because state lives in the hash; avoid pasting secrets into the pattern or test fields.
Embed in your docs
Add the tool to an internal wiki or README with an iframe. The embed URL hides the site header and footer; state still lives in the hash.
Replace the host with yours when self-hosting. Open embed page