Online JavaScript Regex Tester
Test and debug JavaScript regular expressions in real time. See highlighted matches, captured groups, flags, and replace output before you paste a pattern into Node.js, browser code, validation rules, or cleanup scripts.
How to Use This Regex Tester
Enter your regex pattern in the pattern field and your test text in the text area below. Matches are highlighted in real-time as you type. Toggle flags (g, i, m, s) to modify matching behavior. Use Replace mode to test string replacements with capture group references ($1, $2). Click any common pattern button to quickly load frequently used regex patterns.
Regex Flags
g (global) matches all occurrences, not just the first. i (case-insensitive) ignores letter case. m (multiline) makes ^ and $ match line boundaries. s (dotAll) makes . match newline characters.
Common online regex checks you can run here
Use this page as a quick JavaScript regex sandbox before pasting a pattern into code, forms, analytics filters, or content cleanup scripts.
- Validate common formats
Try email, URL, US phone, IPv4, hex color, and date patterns from the built-in pattern library.
- Debug capture groups
Check exactly what each group returns before using $1, $2, or named logic in your app.
- Preview find and replace
Switch on replace mode to test cleanup rules for text, CSV snippets, logs, or copied HTML.
- Keep private text local
Matching runs in your browser, so sample text is not uploaded to Toolflix.
JavaScript regex tester for real workflows
Match behavior follows the browser JavaScript RegExp engine, so it is a practical preview for frontend validation, Node.js scripts, log cleanup, URL parsing, and quick one-off text fixes.
Try email, URL, date, phone, IP address, and hex color patterns.
Confirm capture groups and match indexes before writing code.
Test find-and-replace rules with $1 and $2 output safely.
Frequently Asked Questions
Is my data safe?
Yes. All regex matching happens in your browser. No data is sent to any server.
Which regex engine is used?
This tool uses JavaScript's built-in RegExp engine, which follows the ECMAScript specification. Syntax and behavior match what you would get in Node.js or any modern browser.
Can I test regex replace output?
Yes. Turn on Replace mode, enter a replacement string, and preview the result before using the expression in JavaScript, Node.js, or browser code.
Can I debug JavaScript capture groups?
Yes. Matching details show the full match, index, and captured groups so you can verify how $1, $2, and similar replacement references will behave.
Is this an online regex tester or a server-side checker?
It is an online tool, but the matching runs locally in your browser. Toolflix does not upload your pattern or test text to a server.