Regular Expression Tester

Test and debug regular expressions in real-time

/ /

Enter a regular expression to begin testing

Common Patterns (Click to use)

Test String

Match Results

Matched portions will be highlighted here...

Regular Expression Cheatsheet

Character Classes

. Any character

\d Digit [0-9]

\w Word [A-Za-z0-9_]

\s Whitespace

[abc] a, b, or c

[^abc] Not a, b, or c

Quantifiers

* 0 or more

+ 1 or more

? 0 or 1

{n} Exactly n

{n,} n or more

{n,m} Between n and m

Anchors

^ Start of string

$ End of string

\b Word boundary

Groups

(abc) Capture group

(?:abc) Non-capture group

a|b a or b

What is Regex Tester?

A regex tester helps you validate regular expressions against sample text so you can debug patterns faster and avoid trial-and-error in production code.

Regex Tester helps when you need Test regex patterns in one tab instead of switching to desktop software or a temporary script.

How to use this tool

Paste your regex pattern and sample text into the tool.
Toggle the flags you need such as global, multiline, or case-insensitive mode.
Review matches, groups, and misses until the pattern behaves as expected.

Common use cases

Debugging validation rules for forms and API inputs.
Testing search-and-replace patterns before using them in an editor.
Teaching or documenting how a regex behaves with real sample data.

Tips for better results

Start with a narrow sample string, then test noisy real-world input.
Check edge cases such as empty values, spacing, and punctuation.
Document the final pattern together with example matches.

Example workflow

Pattern: ^[a-z0-9_]{3,16}$\nText: user_name_01

FAQ

Why use a regex tester?

It gives instant feedback on matches so you can adjust a pattern before it ships to code or content workflows.

Should I test regex with real sample data?

Yes. Synthetic samples help at first, but real inputs reveal spacing, casing, and punctuation issues much faster.

What usually breaks a regex pattern?

Flags, anchors, greedy groups, and unescaped special characters are common sources of unexpected matches.