What is a regular expression (regex)?

A regular expression (regex) is a sequence of characters that defines a search pattern. A regex tester lets you apply these patterns to text in order to find, extract, or validate content — from simple word searches to complex email or date format matching.

How do I test a regex pattern online?

Paste your pattern into the regex field and your target text into the input area. The online regex tester instantly highlights all matches in real time, shows captured groups, and reports the total number of matches — no need to write test scripts or run code locally.

What are some common regex patterns I should know?

Widely used patterns in any regex tester include `\d+` for one or more digits, `[a-zA-Z]+` for alphabetic words, `^\S+@\S+\.\S+$` for basic email validation, `\b\d{4}-\d{2}-\d{2}\b` for ISO dates, and `https?://[^\s]+` for URLs. The common patterns library in this tool provides these and more with one click.

What is the difference between regex and glob patterns?

Glob patterns (like `*.txt`) are a simplified syntax used mainly for file name matching in shells and build tools, where `*` means "any characters" and `?` means "one character." A regex tester works with full regular expressions, which are far more expressive — supporting character classes, quantifiers, lookaheads, and groups — and are used across programming languages and text editors.

Is regex syntax the same across all programming languages?

Core regex syntax is similar across most languages, but there are dialect differences. JavaScript (used by this regex tester) supports flags like `g` (global), `i` (case-insensitive), `m` (multiline), and `s` (dotAll). Features like lookbehind assertions, named groups, and atomic groups vary by language, so always verify patterns in the target runtime before deploying.

Regex Tester — Free Online Regular Expression Tool

Regex Tester

Test and debug regular expressions with real-time match highlighting.

Processed locally in your browser

Test and debug regular expressions with real-time match highlighting using this free online regex tester.

Common Patterns

Pattern

Flags

Test String

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How to Use

Test and debug regular expressions with real-time match highlighting using this free online regex tester.

Enter your regex pattern. Type your regular expression into the pattern field at the top. The tool validates the syntax in real time and shows an error message if the pattern is invalid.
Set flags. Toggle the regex flags you need — g (global), i (case-insensitive), m (multiline), and s (dotAll) — using the flag buttons next to the pattern input.
Enter test text. Paste or type the text you want to match against into the test string area. All matches are highlighted instantly as you type.
Inspect matches. The results panel shows every match with its index, matched text, and any captured groups. This makes it easy to verify that your pattern captures exactly what you intend.
Browse the cheatsheet. Use the built-in reference for common regex syntax — character classes, quantifiers, anchors, groups, and lookaheads — without leaving the page.

This regex tester uses the JavaScript regex engine (the same one running in your browser and Node.js). Patterns tested here will work directly in JavaScript code. No data is sent to any server.

Features

✓Real-time match highlighting
✓Flag toggles (g, i, m, s)
✓Capture group display
✓Common patterns library
✓Match count and details
✓Error feedback

Frequently Asked Questions

What is a regular expression (regex)?: A regular expression (regex) is a sequence of characters that defines a search pattern. A regex tester lets you apply these patterns to text in order to find, extract, or validate content — from simple word searches to complex email or date format matching.
How do I test a regex pattern online?: Paste your pattern into the regex field and your target text into the input area. The online regex tester instantly highlights all matches in real time, shows captured groups, and reports the total number of matches — no need to write test scripts or run code locally.
What are some common regex patterns I should know?: Widely used patterns in any regex tester include `\d+` for one or more digits, `[a-zA-Z]+` for alphabetic words, `^\S+@\S+\.\S+$` for basic email validation, `\b\d{4}-\d{2}-\d{2}\b` for ISO dates, and `https?://[^\s]+` for URLs. The common patterns library in this tool provides these and more with one click.
What is the difference between regex and glob patterns?: Glob patterns (like `*.txt`) are a simplified syntax used mainly for file name matching in shells and build tools, where `*` means "any characters" and `?` means "one character." A regex tester works with full regular expressions, which are far more expressive — supporting character classes, quantifiers, lookaheads, and groups — and are used across programming languages and text editors.
Is regex syntax the same across all programming languages?: Core regex syntax is similar across most languages, but there are dialect differences. JavaScript (used by this regex tester) supports flags like `g` (global), `i` (case-insensitive), `m` (multiline), and `s` (dotAll). Features like lookbehind assertions, named groups, and atomic groups vary by language, so always verify patterns in the target runtime before deploying.

Regex Tester

How to Use

Features

Frequently Asked Questions

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