Email validation
/^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/Simple email shape check  not RFC-compliant, but practical.
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Regex Tester with Real Examples + Cheatsheet + Use Cases
Test regex with practical examples, quick cheatsheet patterns, and common use cases.
About Regex Tester with Real Examples + Cheatsheet + Use Cases
Regex Tester lets you build, test, and debug regular expressions against real text in real time. Type a pattern and matches highlight instantly, with capture groups, named groups, and named backreferences shown side-by-side.
Built on the browser native RegExp engine, it supports all standard ECMAScript regex flags (g, i, m, s, u, y) and the lookahead, lookbehind, and character class features you would expect.
Features
Live highlighting
Every match and capture group is highlighted as you type.
All ECMAScript flags
Global, case-insensitive, multiline, dotall, unicode, sticky.
Capture groups
Numbered and named groups extracted into a clear table.
Replace mode
Run substitutions with $1, $2, and $<name> references.
Pattern explanation
Each token (anchor, quantifier, character class) explained inline.
Test multiple inputs
Paste a multi-line input and see matches across all lines.
How to use Regex Tester with Real Examples + Cheatsheet + Use Cases
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1
Enter a pattern
Type your regex in the pattern field, with or without delimiters.
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2
Pick flags
Toggle global, case-insensitive, multiline, etc.
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3
Paste test input
Drop in the text you want to match against.
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4
Read results
Matches highlight in real time, and capture groups appear in a table.
Examples
Extract URLs
/https?:\/\/[^\s]+/gPull every URL out of a block of text.
Named groups
/(?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2})/Parse ISO dates with named capture groups.
When to use Regex Tester with Real Examples + Cheatsheet + Use Cases
- Validating user input (emails, phone numbers, dates) before submitting forms
- Extracting structured data from logs, raw text, or scraped HTML
- Refactoring code with find-and-replace across many files
- Writing routes, redirects, and URL rewrites for nginx, Apache, or Cloudflare
- Building grep-style patterns for grep, ripgrep, sed, or any tool that uses ECMAScript-compatible regex
When to use Regex Tester
Use it when
Use Regex Tester when you need fast live regex highlighting, match counts, indexes, and common pattern presets in the browser.
Do not use it when
Do not use regex as your only validation for complex formats or security-sensitive parsing. Prefer formal parsers where available.
Frequently Asked Questions
Which regex flavor does this use?
ECMAScript / JavaScript regex, the same flavor your browser uses for String.prototype.match and RegExp. It is similar to PCRE but does not support recursive patterns, conditional regex, or possessive quantifiers.
Are my patterns and test text private?
Yes. Everything runs locally with no network calls. Your patterns and the text you test against never leave your browser.
Does it support lookbehind?
Yes. Modern browsers support both lookahead (?=...) and lookbehind (?<=...), including the negative variants. Older browsers (pre-2019) may not support lookbehind.
How do I match across multiple lines?
Add the m flag to make ^ and $ match at line boundaries. Add the s flag to make . match newlines. Together they cover most multi-line use cases.
How do I escape special characters?
Prefix with a backslash. The metacharacters that need escaping are . ^ $ * + ? ( ) [ ] { } | and the backslash itself.
Why is my pattern slow?
Catastrophic backtracking. Patterns like (a+)+b against a long string of as explode in runtime. Use possessive-style alternatives, atomic groups (where supported), or rewrite with non-overlapping alternatives.
Can I use this for replace?
Yes. Switch to replace mode and use $1, $2 for numbered groups or $<name> for named groups in the replacement string.
Need a different tool?
Kitpace ships 80+ free, browser-based tools for developers, designers, marketers, and everyday tasks. No signup, no tracking, no fees.
Validating user input (emails, phone numbers, dates) before submitting forms
Type your regex in the pattern field, with or without delimiters.
Every match and capture group is highlighted as you type.
Recommendation FAQs
Does Regex Tester upload my text?
No. Regex matching runs locally in the browser.
Does it highlight regex matches?
Yes. Regex Tester highlights matches live in the test text.
Can I use preset regex patterns?
Yes. Regex Tester includes common presets like email, URL, date, phone, UUID, color, and JWT.
Last updated: May 2026. Maintained by: Kitpace.
Quick answer
Regex Tester by Kitpace is a free browser-based regular expression tester. It highlights matches live, supports regex flags, includes common presets for email, URL, dates, phones, UUIDs, colors, JWTs, and files, and shows match indexes without signup.