Developer Tools
Regex Tester
Test regular expressions against sample text with real-time match highlighting.
Privacy guaranteed. Your files and text are processed securely and are never permanently stored on our servers.
Free Online Regex Tester
Regular expressions (Regex) are incredibly powerful for parsing text, validating user input, and extracting data. However, writing them is notoriously difficult, and a single misplaced character can lead to catastrophic bugs. Our free online regex tester provides a visual sandbox where developers can write, test, and debug their regular expressions in real-time against sample text.
Real-Time Match Highlighting
Stop guessing if your regex actually works. As you type your pattern into our regex checker, the tool instantly highlights every match within your test text. It allows you to quickly toggle flags like global (g), case-insensitive (i), and multiline (m) to see how they affect the parsing logic. This immediate feedback loop is essential for building complex patterns for email validation, password strength checks, or data scraping.
100% Private Browser Execution
If you are testing regex against proprietary log files, customer databases, or sensitive code snippets, security is paramount. Unlike server-side regex debuggers, our tool executes the regex engine natively within your web browser using standard JavaScript (ECMAScript) regex specifications. Your patterns and test data never leave your device, guaranteeing bank-grade security.
FAQ
How do I test a regular expression?+
Type your regex pattern in the top input field, select your flags (like 'g' or 'i'), and paste your sample text into the main editor. The tool will instantly highlight any matches.
Which regex flavor does this tool use?+
Our tool utilizes the standard JavaScript (ECMAScript) regex engine built directly into your web browser, which is heavily compatible with PCRE, Python, and Java regex patterns.
Is it safe to paste sensitive logs here?+
Yes, it is 100% safe. The regex evaluation happens entirely locally on your device. Your sensitive log files are never transmitted to our servers.
What does the 'g' flag do?+
The 'g' (global) flag tells the regex engine to find all matches in the text, rather than stopping after it finds the very first match.
What does the 'i' flag do?+
The 'i' (ignore case) flag makes the regex case-insensitive, meaning 'A' will match 'a', and vice versa.
Why is my regex not matching?+
Common issues include forgetting to escape special characters (like . or *), not using the global flag, or using a feature not supported by the JavaScript regex engine (like lookbehinds in older browsers).
Does it support capturing groups?+
Yes, the engine processes capturing groups. While the visual highlighter shows the full match, capturing groups work exactly as they would in a standard JavaScript environment.
Can I use this to validate emails?+
Yes, you can write and test email validation patterns here to ensure they correctly accept valid emails and reject invalid ones based on your sample data.
Is this tool free?+
Yes, our regex tester is completely free for all developers with no usage limits.
Will this slow down if I paste a huge text file?+
Because it runs in the browser, extremely large texts combined with poorly optimized regex patterns (which cause catastrophic backtracking) may temporarily freeze the page.