Regular Expression

Test String

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UTF-8

Match Details

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Enter a regex and test string

Real-time Matching

See matches instantly as you type. Visual highlighting shows exactly what your regex captures.

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All processing happens in your browser. No data is ever sent to a server.

Learn Regex

Built-in explanations break down each token. Quick recipes for common patterns.

What Is Regex Tester?

Regex Tester is a free online tool that lets you test, debug, and visualize regular expressions in real-time. It runs entirely in your browser — no data is ever sent to a server — giving you instant feedback with visual highlighting, match details, capture group analysis, and code export.

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Key Features

  • Real-time matching with visual highlighting as you type
  • Flag toggles for Global (g), Case Insensitive (i), and Multiline (m) modes
  • Match details table showing full matches, capture groups, and index ranges
  • Pattern explanation that breaks down each regex token into plain language
  • Quick recipes for common patterns: Email, URL, Phone, Password, Date, IPv4, HTML Tags, Hex Colors, and Credit Cards
  • Export code snippets for JavaScript, Python, PHP, Go, and Rust
  • Debounced input for smooth performance with complex patterns

How to Use

Enter your regular expression pattern in the editor at the top. Toggle flags (g, i, m) using the Flags dropdown. Type or paste your test string in the bottom panel. Matches are highlighted in real-time and detailed in the right sidebar. Use Quick Recipes to load common patterns instantly, or export your regex as production-ready code in 5 languages.

Common Use Cases

  • Validating email addresses, phone numbers, URLs, and IP addresses
  • Extracting data from log files and structured text
  • Building and testing search patterns for find-and-replace operations
  • Matching HTML tags, hex color codes, and credit card numbers
  • Learning regex syntax with the built-in pattern explanation feature
  • Generating regex code snippets for JavaScript, Python, PHP, Go, and Rust projects

Frequently Asked Questions

Is my data sent to any server?
No. All regex matching and processing happens entirely in your browser using JavaScript. Your test strings and patterns never leave your device.
Which regex engine does this use?
This tool uses the JavaScript RegExp engine built into your browser. Syntax and behavior may differ slightly from other engines (PCRE, Python re, etc.).
Can I test multiline strings?
Yes. Enable the "m" (Multiline) flag to make ^ and $ match the start and end of each line. You can paste multiline text directly into the test string area.
What are capture groups?
Capture groups are portions of a regex pattern enclosed in parentheses ( ). They let you extract specific parts of a match. The Match Details table shows each group's content and index.