Regex Tester & Visualizer – Free Online

Name: Interactive Regex Tester & Visualizer
Brand: ToolLok

Back to All Tools

Interactive Regex Tester

100% Free

Write, test, debug, replace, inspect, and export JavaScript regular expressions in real-time.

Regular Expression

flags

JavaScript RegExp syntax. Pattern and test data stay in your browser.

Test String0 Matches

76 chars

Match Inspector

Matching results and capture groups will appear here.

Find & Replace

JavaScript replacement syntax

Replacement

Preview

Contact [EMAIL] or [EMAIL]. Invalid: admin@.com

Export Code

const pattern = "[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,}";
const flags = "g";
const regex = new RegExp(pattern, flags);
const string = "Contact support@example.com or sales-team@codemines.com. Invalid: admin@.com";

// Get the first match
const firstMatch = regex.exec(string);
console.log("First match:", firstMatch?.[0] ?? null);

// Get all matches
regex.lastIndex = 0;
const matches = Array.from(
  string.matchAll(
    new RegExp(
      pattern,
      flags.includes("g") ? flags : flags + "g"
    )
  )
);

console.log(
  "Matches:",
  matches.map((match) => match[0])
);

Exports use safe string escaping. Python and Go snippets note JavaScript flags that do not have direct equivalents.

Execution safety

Regex matching runs inside a temporary Web Worker and is terminated after a short execution budget. This helps prevent an expensive pattern from freezing the page. Very complex expressions may still need optimization.

Master Regular Expressions with the Interactive Regex Tester

Writing Regular Expressions (Regex) can be frustrating without visual feedback. ToolLok's Interactive Regex Tester evaluates patterns and flags in real-time, highlights exact matches, and lets you inspect capture groups. Use it for validation, parsing logs, extracting data, testing replacements, and preparing production-ready regex snippets for your Developer Tools workflow.

Key Features

Live Match Debugging: See matches, positions, zero-length matches, numbered groups, and named groups.
Find & Replace: Preview replacements and apply the first match or all matches.
Code Export: Generate safely escaped JavaScript, Python, and Go examples.
Regex Presets: Start quickly with common email, URL, IP, UUID, date, phone, color, and password patterns.
Browser Privacy: Regex patterns and test strings are processed locally in the browser.

Frequently Asked Questions

What does the "g" flag mean in Regex?

The "g" flag means global matching. It allows the JavaScript regex engine to find multiple matches instead of stopping after the first match.

Are my Regex patterns logged?

The Regex Tester performs matching in your browser. This component does not send your regex pattern or test string to a ToolLok API.

How to use Interactive Regex Tester & Visualizer

1Type your Regular Expression pattern into the top input field.
2Add any necessary flags (like 'g' for global or 'i' for case-insensitive) in the flags box.
3Type or paste your test strings into the main editor window.
4Watch the test string highlight your matches in real-time. Use the right sidebar to copy code snippets for your preferred language.

About Interactive Regex Tester & Visualizer

Test regular expressions in real time, see matches highlighted and get a plain-English breakdown of the pattern. Works in your browser with JavaScript regex.

This tool runs in your browser. Anything you enter is processed on your device. See our Privacy Policy.

View all

Interactive Regex Tester & Visualizer

Interactive Regex Tester

Execution safety

Master Regular Expressions with the Interactive Regex Tester

Key Features

Frequently Asked Questions

What does the "g" flag mean in Regex?

Are my Regex patterns logged?

How to use Interactive Regex Tester & Visualizer

About Interactive Regex Tester & Visualizer

More Developer Tools

Interactive Regex Tester

Execution safety

Master Regular Expressions with the Interactive Regex Tester

Key Features

Frequently Asked Questions

What does the "g" flag mean in Regex?

Are my Regex patterns logged?