Free online regex tester and debugger. Test regular expressions with real-time matching, flags (g, i, m, s, u, y), match groups, lookahead/lookbehind, and replacement testing. Includes built-in regex cheat sheet and common pattern library. Essential for developers. 100% browser-based.
100% browser-based — your data never leaves your device
Test regular expressions with real-time matching, syntax highlighting, and cheat sheet.
user@example.com admin@test.org invalid-email
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Regex TesterTest regular expressions with real-time matching, syntax highlighting, and cheat sheet.
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Regex Tester is a free online text tool that test regular expressions with real-time matching, syntax highlighting, and cheat sheet. It works entirely in your browser — no downloads, no installations, and no server uploads required. content writers, developers, technical writers use Regex Tester when they need a fast, privacy-respecting way to process text data without installing additional software. It supports capabilities such as live matching, flags support, match details. Additional features include replace tool. Common use cases include debugging and testing regular expressions before deploying to production code, validating input patterns like email, phone, and postal code formats, extracting structured data from unstructured text using capture groups. All processing happens locally using modern browser APIs, which means your data never leaves your device. This makes Regex Tester ideal for working with sensitive data, proprietary code, or any situation where privacy matters.
Regex Tester is a free online text tool that helps you test regular expressions with real-time matching, syntax highlighting, and cheat sheet. Key capabilities include live matching, flags support, match details. All processing is done locally in your browser — no data is uploaded, stored, or shared with any server. There are no sign-ups, no file size limits, and no hidden charges. It is commonly used to debugging and testing regular expressions before deploying to production code.
Type your regular expression in the pattern field (without delimiters).
Paste the text you want to test against in the test string area.
Enable flags like g (global) or i (case-insensitive) and see matches highlighted in real-time with match details.
| Category | Details |
|---|---|
| Input Limits | Maximum input length: Browser memory bound |
| Encoding support: UTF-8, UTF-16, ASCII, ISO-8859-1, Windows-1252 | |
| Supported Formats | Plain text, UTF-8, ASCII, Unicode, Percent-encoding (RFC 3986) |
| Browser Engine |
|
All operations run entirely in your browser using built-in Text APIs. No server uploads, no data storage, and no third-party requests.
Regex Tester is ideal when you need to debugging and testing regular expressions before deploying to production code without installing software or uploading data to a server. Since everything runs in your browser, there is no setup time and no risk of your data being stored on external servers. For for advanced text manipulation within an IDE, consider using VS Code. For for batch text processing on servers, sed/awk (command-line) may be a better fit. Regex Tester fills the gap between heavyweight desktop tools and insecure online services that require uploading your data.
No. Regex Tester processes everything entirely in your browser using JavaScript. Nothing you type, paste, or upload is ever transmitted to any server. Your data never leaves your device.
No. All regex testing happens locally in your browser.
JavaScript's built-in RegExp engine, consistent with Node.js and browser environments.
See regex matches highlight in real-time as you type your pattern and test string.
Toggle global, case-insensitive, multiline, dotall, unicode, and sticky flags.
View each match's index, groups, and capture group values.
Test regex replacements live before using in code.
Regex Tester is useful in a variety of scenarios across different workflows:
Debugging and testing regular expressions before deploying to production code
Validating input patterns like email, phone, and postal code formats
Extracting structured data from unstructured text using capture groups
Begin with a basic pattern that matches your target, then gradually add features like lookaheads and quantifiers. Test each addition incrementally.
The g flag finds all matches, i makes it case-insensitive, and m changes ^ and $ to match line boundaries. Combine flags for powerful pattern matching.
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