Regex Tester

🧩 JavaScript Regex Tester — Instant, Private, Client-Side

Test, debug, and save JavaScript regular expressions right in your browser — multi-tab editor, real-time highlights, and IndexedDB session saves. No servers. No tracking.

⚡ Why Choose Our Regex Tester?

• 🖥 Client-Side Only — All data stays in your browser (IndexedDB).
• 🗂 Multi-Tab Editor — Compare patterns and test strings side by side.
• 💾 Save & Load Sessions — Pick up where you left off anytime.
• 🔍 Instant Highlights — Matches and capture groups shown in real-time.
• 📜 Export JS Snippets — Copy tested regex directly into your code.
• 📚 Cheat Sheet & Examples — Common patterns ready to use.

🛠 Features

• Real-Time Matching: See matches and capture groups instantly.
• Quick Copy: Export patterns to JavaScript easily.
• Pattern Library: Preloaded examples for email, URL, phone, IP, and more.
• Private & Offline: No server required; fully offline-compatible.
• User-Friendly UI: Lightweight, responsive, multi-tab interface for devs.

🧰 Quick Cheat Sheet — How & When to Use It

Regular expressions can be intimidating at first. This cheat sheet breaks down flags, characters, classes, groups, and quantifiers and shows how and when to use them.

🔹 Flags (modifiers)

Flags modify the behavior of your regex. Always choose flags based on what you want to match.

Tip: Use g when replacing or finding multiple matches. Use i for user input that may vary in case.

🔹 Special Characters

Special characters allow you to match characters literally or escape their special meaning.

Tip: Use `` when you want to match symbols like ., *, ?, +, (, ) literally.

🔹 Character Classes

Character classes match sets or ranges of characters.

Tip: Use d for numbers, w for identifiers, and s to trim or detect spaces.

🔹 Groups & Captures

Groups let you capture parts of a match or apply quantifiers to multiple characters.

Tip: Use capturing groups when you need to extract data, non-capturing to just group for repetition without storing matches.

🔹 Quantifiers

Quantifiers define how many times a pattern should repeat.

Tip: Use {n,m} for flexible lengths, */+ for optional repeats, and ? for optional characters.

✅ How to Use Cheat Sheet Effectively

1. Identify your need: What do you want to match? A number, email, URL, or custom string?
2. Pick the right flags: Case-sensitive, global, or multiline?
3. Use character classes: d for digits, w for words, s for spaces.
4. Group strategically: Capture what you need, repeat with non-capturing if needed.
5. Test & refine: Use the Regex Tester live — tweak patterns and flags until your matches are correct.
6. Export safely: Copy your tested regex into JS code for production.

Example:

• Want to validate a US phone number with optional country code:

/^+?1?s*(?d{3})?[-.s]?d{3}[-.s]?d{4}$/

• Use ^ & $ to anchor the match, ? for optional parts, d for digits, s to allow spaces.

📋 Commonly Used Regex Patterns

✅ Tip: You can click or copy these patterns directly into your regex tester for instant testing.

💡 How to Script Your Regex in JavaScript

Basic match:

const pattern = /^[^s@]+@[^s@]+.[^s@]+$/;
const text = "alice@example.com";
console.log(pattern.test(text)); // true/false

Get all matches with capture groups:

const re = /(d{4})-(d{2})-(d{2})/g;
const str = "2025-01-01 and 2024-12-31";
const matches = [...str.matchAll(re)];
matches.forEach(m => console.log(m[0], 'Year:', m[1]));

Replace matches dynamically:

const re = /(w+)@example.com/gi;
const s = "Contact: alice@example.com, bob@example.com";
const res = s.replace(re, (match, name) => `${name}@company.com`);
console.log(res);

Create regex safely from user input:

function escapeForRegExp(str) {
  return str.replace(/[.*+?^${}()|[]\]/g, '\$&');
}
const userInput = "foo.bar";
const safeRe = new RegExp(escapeForRegExp(userInput), "gi");

💾 Save Sessions in Browser (IndexedDB)

async function saveSession(session) {
  const db = await openDB('regex-tester', 1);
  const tx = db.transaction('sessions','readwrite');
  tx.objectStore('sessions').put(session);
  return tx.complete;
}
 
saveSession({
  id: 'session-1',
  created: Date.now(),
  tabs: [{ title:'Example', pattern:'/a/g', text:'abc' }]
});

✅ Fully client-side, private, and offline.

❓ Frequently Asked Questions (FAQ)

Q1: Which regex flavor is supported?

• Our tester supports JavaScript (ES2018+) regex only. Other flavors like PCRE or Python are not supported yet.

Q2: How is my data saved?

• All sessions are stored in IndexedDB in your browser. Nothing is sent to our servers — your data remains private.

Q3: Can I use multiple tabs?

• ✅ Yes! You can create and switch between multiple tabs for different patterns and test strings.

Q4: How do I export a regex to my code?

• Click Export and copy the JavaScript snippet with your regex and flags, ready to use in your application.

Q5: Can I use it offline?

• Absolutely. Once the page is loaded, everything works offline, including session saving.

Q6: Are there ready-made patterns?

• Yes! We provide a pattern library with email, URL, phone, IP, hex colors, passwords, dates, and more.

🌟 Call-to-Action

• [Try the Regex Tester Now]
• [Load Example Patterns]
• [Save Your Session]

📚 Learn Regex Step by Step

New to regular expressions? The Regex Tutorials series walks you through 22 lessons — from literal characters to lookaheads — with a runnable tester on every example. Each lesson builds directly from this tester, so you can apply what you learn instantly.

• Client-side regex tester JavaScript
• Offline regex tester browser save sessions
• Multi-tab regex editor for developers