Developer Tool

Regex tester & generator

Build and test regular expressions live in your browser. Optional Python re check when you need server-side flavor parity.

Live tester JavaScript

//

Ready.

#MatchIndexGroups
Matches appear here.

Python re check

Optional — same pattern against Python’s engine (flags: i m s x a). Live panel above stays JavaScript.

Enter the correct answer.
Today’s tool allowance
  • Runs: 10 left of 10

Create a free account or see plans for higher limits.

Quick cheatsheet

. any char · \d digit · \w word · \s space
* 0+ · + 1+ · ? optional · {n,m} range
^ start · $ end · () group · (?:) non-capturing

Regex tester and pattern generator

Regular expressions help you validate emails, extract IDs, clean whitespace, and rewrite text in code and content workflows. This tool lets you experiment live in the browser, load common presets, escape literal strings safely, and optionally confirm the same pattern with Python’s re engine when you need server-side flavor checks.

What you can do

  • Test patterns with live highlighting, match lists, and capture groups
  • Toggle flags such as global, ignore-case, multiline, and unicode
  • Try replace mode with $1 / $& style substitutions
  • Generate starters from presets (email, URL, IPv4, dates, slugs, and more)
  • Build simple character classes and escape user-facing text into a safe pattern

JavaScript vs Python

The main panel uses JavaScript RegExp for instant feedback. Dialects differ — lookbehinds, verbose mode, and some escapes behave differently in Python. Use Test with Python when your production code runs on Flask, Django, Magento helpers, or other Python tooling.

Tips for better patterns

  • Start specific, then relax — over-broad patterns create false positives
  • Prefer non-capturing groups (?:…) when you do not need the capture
  • Anchor with ^ / $ for whole-string validation
  • Never paste secrets into public tools on shared devices

Frequently asked questions

Is live testing counted against my daily quota?

No. Instant JavaScript testing runs in your browser. Only the optional Python check uses captcha/quota rules like other developer tools.

Will a preset fully validate emails or URLs?

Presets are practical starters, not full RFC validators. Tune them for your product rules.

Can I use this offline?

Once the page is loaded, the live tester works without further network calls. Python checks require a form submit.