Regex Tester

Live Testing

Test regular expressions with live highlighting and match groups

Regular Expression

//g

Flags:g(global)i(case-insensitive)m(multiline)s(dotAll)

Common Patterns

EmailURLPhoneIPv4Hex ColorDate (YYYY-MM-DD)NumbersWords

Test String

What is Regex Tester?

The Regex Tester is an interactive tool designed for building, testing, and debugging Regular Expressions. It provides real-time highlighting of matches within a test string, making complex pattern matching easier to understand.

How to Use Regex Tester

Enter Pattern

Type your regular expression pattern in the designated input field.

Select Flags

Toggle common flags like 'g' (global), 'i' (case-insensitive), or 'm' (multiline).

Input Test Text

Paste the text you want to search against into the text area.

View Matches

Observe the live highlighting to see exactly what your regex pattern matches.

Key Features

Real-time syntax highlighting for matching text

Support for common regex flags (g, i, m)

Instant feedback on pattern validity and errors

Clear visual separation of capture groups

Works entirely in the browser using JavaScript's regex engine

Tips & Best Practices

1
Start with simple patterns and gradually add complexity while watching the live highlights.
2
Use the 'i' flag if you want your search to ignore capitalization.
3
Rely on capture groups (using parentheses) to extract specific parts of a matched string in your actual code.

Why Use Our Online Regex Tester?

Regex Tester gives developers a fast, distraction-free utility that runs entirely client-side. No accounts, no data sent to any server, no extensions to install. Paste your input, get your output, copy to clipboard — designed to slot into your daily workflow without breaking your flow.

Client-SideCode stays private

Zero SetupNo installs needed

Copy to ClipboardOne-click workflow

Open StandardsCommon formats

Frequently Asked Questions

Which Regex flavor does this tool use?

The tool utilizes the JavaScript (ECMAScript) regular expression engine, as it runs natively within your web browser.

Can I save my regex patterns?

Currently, patterns are not saved permanently. We recommend copying successful patterns directly into your codebase.

Why is my pattern causing the browser to freeze?

Certain complex regex patterns can cause 'Catastrophic Backtracking' in the engine. Try simplifying the pattern if performance degrades.

Does it explain what the regex does?

While it provides live highlighting of matches, it currently does not generate an English explanation of the syntax elements.

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