Regex Tester & Builder

Q: Is my test text uploaded?

No. Everything runs locally in your browser using standard web APIs — your text, files and inputs are never uploaded to a server, so the tool works even offline once the page has loaded.

Q: Which regex flavour does it use?

It uses JavaScript (ECMAScript) regular expressions, including flags like global, case-insensitive and multiline, which closely match most other languages for common patterns. Most common regex syntax (character classes, quantifiers, anchors, alternation) works identically across JavaScript, Python, Perl and most other regex engines, so you can test patterns here and use them in your production code with minimal translation. More advanced features like lookahead/lookbehind and named captures also have wide support in modern languages. If you're writing regex for a different language with different features, test your specific edge cases to ensure compatibility.

Q: Can it explain what a pattern does?

The presets give you working patterns for common tasks, and live highlighting shows exactly what each part matches as you tweak it. By selecting preset patterns for email, URL, phone, or date validation, you get tested regex expressions you can adapt rather than building from scratch. The live highlighting feature color-codes which parts of your sample text match each portion of the regex pattern, giving you immediate visual feedback as you edit. This trial-and-error approach with instant feedback is much faster than reading documentation or guessing at regex syntax.

Test patterns against text and build common regex from presets.

Processed locally — nothing is uploaded

Test

2 matches

Contact ada@example.com or grace@navy.mil — replies within 13 days.

Capture groups

Match 1 @ 8: ada@example.com

$1 ada$2 example$3 com

Match 2 @ 27: grace@navy.mil

$1 grace$2 navy$3 mil

Explanation

(
Group — a capturing group
\w
Character class — matches a word character (a–z, A–Z, 0–9, _)
+
Quantifier — matches the preceding token one or more times
)
Group — end of the group
@
Literal — the character "@" literally
(
Group — a capturing group
\w
Character class — matches a word character (a–z, A–Z, 0–9, _)
+
Quantifier — matches the preceding token one or more times
)
Group — end of the group
\.
Character class — matches the character "." literally
(
Group — a capturing group
\w
Character class — matches a word character (a–z, A–Z, 0–9, _)
+
Quantifier — matches the preceding token one or more times
)
Group — end of the group

Build from preset

Email address
[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}
URL
https?:\/\/[\w.-]+(?:\/[\w./?%&=-]*)?
IPv4 address
\b(?:\d{1,3}\.){3}\d{1,3}\b
IPv6 address
(?:[A-Fa-f0-9]{1,4}:){2,7}[A-Fa-f0-9]{1,4}
MAC address
(?:[0-9A-Fa-f]{2}[:-]){5}[0-9A-Fa-f]{2}
UUID v4
[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}
Date (YYYY-MM-DD)
\d{4}-(?:0[1-9]|1[0-2])-(?:0[1-9]|[12]\d|3[01])
Time (HH:MM 24h)
(?:[01]\d|2[0-3]):[0-5]\d
Hex color
#(?:[0-9a-fA-F]{3}|[0-9a-fA-F]{6})\b
Phone number
\+?\d[\d\s().-]{7,}\d
US ZIP code
\b\d{5}(?:-\d{4})?\b
Strong password
(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[^\w\s]).{8,}
Slug
[a-z0-9]+(?:-[a-z0-9]+)*
HTML tag
<\/?[a-zA-Z][\w-]*(?:\s[^<>]*)?>
Hashtag
#[A-Za-z0-9_]+
Floating point
[-+]?\d*\.?\d+(?:[eE][-+]?\d+)?
Digits only
\d+
Words
\b\w+\b

Cheat sheet

.	Any character except newline
\d \w \s	Digit, word char, whitespace
\D \W \S	Negated digit / word / whitespace
[abc]	Any of a, b or c
[^abc]	Anything except a, b or c
[a-z]	Character range a to z
^ $	Start / end of string (or line with m)
\b	Word boundary
* + ?	0+, 1+, 0 or 1 of the previous
{n} {n,} {n,m}	Exactly / at least / range repeats
*? +?	Lazy (as few as possible)
(…)	Capturing group
(?:…)	Non-capturing group
(?<name>…)	Named capturing group
(?=…) (?!…)	Positive / negative lookahead
(?<=…) (?<!…)	Positive / negative lookbehind
a\|b	Match a or b
\. \/ \\	Escaped literal . / \

About Regex Tester & Builder

Matches highlight as you type, so you can watch a pattern narrow or blow up with each character you add. The presets cover the expressions people rewrite constantly, as a starting point to adapt rather than trust blindly.

Test regular expressions against sample text with live match highlighting, or build common patterns — emails, URLs, dates, phone numbers — from ready-made presets. As you edit the pattern and flags, matches update instantly so you can refine without guesswork.

It is the quick way to validate a pattern before dropping it into code, or to work out how an unfamiliar one behaves. Test the awkward cases as well as the obvious ones — an empty string, a trailing space, a doubled separator — because those are what fail in production.

Learn how this works

A Practical Guide to Everyday Developer Encoding & FormattingHow and when to use Base64, JSON formatting, hashing, JWTs, regex and cron — with free in-browser tools for each task.11 min read

Frequently asked questions

Is my test text uploaded?

No. Everything runs locally in your browser using standard web APIs — your text, files and inputs are never uploaded to a server, so the tool works even offline once the page has loaded.

Which regex flavour does it use?

It uses JavaScript (ECMAScript) regular expressions, including flags like global, case-insensitive and multiline, which closely match most other languages for common patterns. Most common regex syntax (character classes, quantifiers, anchors, alternation) works identically across JavaScript, Python, Perl and most other regex engines, so you can test patterns here and use them in your production code with minimal translation. More advanced features like lookahead/lookbehind and named captures also have wide support in modern languages. If you're writing regex for a different language with different features, test your specific edge cases to ensure compatibility.

Can it explain what a pattern does?

The presets give you working patterns for common tasks, and live highlighting shows exactly what each part matches as you tweak it. By selecting preset patterns for email, URL, phone, or date validation, you get tested regex expressions you can adapt rather than building from scratch. The live highlighting feature color-codes which parts of your sample text match each portion of the regex pattern, giving you immediate visual feedback as you edit. This trial-and-error approach with instant feedback is much faster than reading documentation or guessing at regex syntax.

Pro Tips

→Build regex patterns incrementally by testing against 10+ sample strings simultaneously and seeing matches highlighted in real-time.
→Use preset patterns for common tasks (email, phone, URL, date formats) as starting points instead of building from scratch.
→Toggle global, case-insensitive, and multiline flags to debug why patterns aren't matching expected strings.
→Export matches and non-matches separately to validate patterns against test datasets before deploying to production code.

Common Use Cases

•Backend developers validating form input patterns (emails, phone numbers, postal codes) before accepting user data.
•Log analysis teams building regex patterns to extract error codes, timestamps, and stack traces from server logs.
•Data engineers cleaning messy datasets by writing patterns to identify and extract phone numbers, addresses, or SKUs.
•Security teams hunting for indicators of compromise in network logs using regex patterns for suspicious IP addresses and domains.

How It Compares

Compared to Regex101.com, our tester includes preset patterns library and faster match highlighting, while offering simpler UX than advanced tools like RegexBuddy that require purchasing licenses, making it ideal for quick pattern validation without learning curve.

Test

Explanation

Build from preset

Cheat sheet

About Regex Tester & Builder

Learn how this works

Frequently asked questions

Pro Tips

Common Use Cases

How It Compares

Related tools

Test

Explanation

Build from preset

Cheat sheet