WALUDO Toolbox
DEVELOP.01 REGEX TESTER

Regex Tester

Live matches · Syntax preview · Explanations · Code generation · Common regex library

REGEX

Regular expression

TEXT

Test text

STATUS / Enter a regular expression to begin
CODE

Code Generator

§ 01

Common Regex Library

Use these frequent regex patterns as starting points. Click any template to load it into the tester.

Numbers

Use
Pattern
Notes

Text

Use
Pattern
Notes

Network

Use
Pattern
Notes

Identity

Use
Pattern
Notes

Date and Time

Use
Pattern
Notes

Encoding and Code

Use
Pattern
Notes
§ 02

Online Regular Expression Tester

Regular expressions are powerful text matching patterns used for search, replace, validation, and extraction across programming languages, editors, and command-line tools.

This online regex tester runs entirely in your browser. Enter a pattern and test text to see live highlights, match positions, capture groups, and replacement previews. The explanation panel turns common regex syntax into readable notes.

The page also includes a library of common regex templates for emails, URLs, IP addresses, dates, IDs, colors, UUIDs, and more. Code generation helps you move the same pattern into JavaScript, Python, Java, PHP, or Go quickly.

§ 03

How to Use the Regex Tester

1
1

Enter a pattern

Type your regular expression and the tool validates it while showing a syntax-colored preview.

2
2

Choose flags

Toggle g, i, m, s, and u to compare global matching, case-insensitive matching, multiline mode, and Unicode mode.

3
3

Paste test text

Add the text you want to inspect. Matching spans are highlighted immediately.

4
4

Review matches

The results panel lists matched text, index, length, and capture groups, with per-match copy controls.

5
5

Read the explanation

The explanation panel translates common tokens, groups, quantifiers, assertions, and anchors into readable notes.

6
6

Generate code

Copy ready-to-use snippets for JavaScript, Python, Java, PHP, and Go.

§ 04

Regex Syntax Cheat Sheet

A compact reference for the regex syntax you will use most often.

Character Classes

Syntax
Meaning
Example
.
Matches any character except a newline
a.b
\d
Matches any digit [0-9]
\d+
\w
Matches letters, digits, and underscores
\w+
\s
Matches whitespace
a\sb
[abc]
Matches any one of a, b, or c
[aeiou]
[^abc]
Matches any character except a, b, or c
[^0-9]

Quantifiers

Syntax
Meaning
Example
*
Matches zero or more times
ab*c
+
Matches one or more times
ab+c
?
Matches zero or one time
ab?c
{n}
Matches exactly n times
\d{3}
{n,}
Matches at least n times
\d{6,}
{n,m}
Matches from n to m times
\d{6,18}

Anchors and Boundaries

Syntax
Meaning
Example
^
Matches the start of a string or line
^Hello
$
Matches the end of a string or line
world$
\b
Matches a word boundary
\bcat\b
\B
Matches a non-word boundary
\Bcat\B

Groups and Assertions

Syntax
Meaning
Example
(...)
Capturing group
(ab)+
(?:...)
Non-capturing group
(?:ab)+
(?=...)
Positive lookahead assertion
\d+(?=USD)
(?!...)
Negative lookahead assertion
\d+(?!USD)
(?<=...)
Positive lookbehind assertion
(?<=\$)\d+
|
Alternation, matching either side
cat|dog

Flags

Syntax
Meaning
Example
g
Global match, find all matches
/pattern/g
i
Case-insensitive matching
/pattern/i
m
Multiline mode, ^ and $ match each line
/pattern/m
s
DotAll mode, . can match newlines
/pattern/s
u
Unicode mode
/pattern/u
§ 05

Regex FAQ

Q1What is a regular expression?

A regular expression is a text pattern made from literal characters and metacharacters. It is used for searching, replacing, validating, and extracting strings.

Q2Does this regex tester upload my data?

No. Matching, highlighting, explanations, replacement previews, and code generation run locally in your browser.

Q3How is JavaScript RegExp different from PCRE?

This tool uses the browser's JavaScript RegExp engine. It is great for front-end and general debugging, but it does not support some PCRE-only features such as recursive patterns.

Q4Why does my regex only match once?

Enable the g flag. Without g, JavaScript RegExp returns only the first match.

Q5Where can I see capture groups?

Each item in the match list displays Group 1, Group 2, and named capture groups when they exist.

Q6Does replace mode support $1 and $2?

Yes. Replacement preview follows JavaScript replace syntax, including $1, $2, and $&.

Q7What is the best way to learn regex?

Start with character classes, quantifiers, anchors, and groups. Then practice with templates and read the explanation panel token by token.

§ 06

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