Regex Tester
Test regular expressions live.
Patrones Comunes
Privacidad 100%
Tus strings de prueba y expresiones regulares nunca se envían a ningún servidor, asegurando que tus datos sensibles (como tokens o logs en los que usas regex) estén seguros en tu RAM.
How do you test a regular expression online?
Docuboxer's regex tester lets you write a regular expression and see it match against your test text in real time — matches light up as you type, and capture groups are broken down so you can see exactly what each parenthesis extracted. It runs on the browser's native ECMAScript (JavaScript) engine, which means the behavior you see here is exactly the behavior your production JavaScript will have: same syntax, same flags, same edge cases. That removes the classic trap of testing in one flavor and deploying in another. The matching runs entirely in your browser, so the text you paste — logs, customer records, source code — never reaches a server, and the tool keeps working offline once the page has loaded. It stays responsive on large test inputs too, since matching is optimized to avoid blocking the page. Free, no signup.
How to use Regex Tester
- Write your regular expression in the top field.
- Paste the test text into the main box.
- Watch matches highlight instantly and analyze the structure of the capture groups.
Common use cases
Extract patterns from heavy logs
Filter IPs, emails or timestamps out of thousands of lines of server logs immediately, refining the pattern until it catches exactly what you need.
Validate frontend form input
Test and refine the exact expression you'll ship in your code to validate names, phone numbers or postal codes — against real sample data, before it reaches users.
Debug a regex that almost works
Paste the pattern and the string it fails on, then tweak character classes and quantifiers with live feedback until every case matches.
Prototype find-and-replace operations
Work out the capture groups for a refactor or data cleanup before running it across a whole codebase or dataset.
Test against sensitive data privately
Logs and datasets often contain personal data. Here the matching runs only in your browser — nothing you paste is uploaded anywhere.
Frequently asked questions
How do I test a regex online for free?
Type the expression in the pattern field, paste sample text below, and matches highlight in real time as you edit either one. Free, no signup, and processed entirely in your browser.
Which regex engine does this tool use?
The browser's native ECMAScript (JavaScript) engine — so the results match exactly what your production JS code will do, including flags and edge-case behavior.
Can I see what my capture groups matched?
Yes. Beyond highlighting whole matches, the tester breaks down each capture group so you can verify that every parenthesized part extracts exactly the fragment you intended.
Does it handle large volumes of test text?
Yes — matching is optimized to run in the background without blocking the browser's main thread, so you can paste thousands of log lines and keep editing smoothly.
Will a regex tested here behave the same in Python or Java?
Mostly, but not always: flavors differ on details like lookbehind, named groups and escape shorthands. This tester is authoritative for JavaScript; for other languages, verify constructs that are flavor-specific.
Is the text I paste sent to a server?
No. Pattern matching runs entirely in your browser's memory — no server, no logs, no retention — and the tool works offline once the page has loaded.