Online Regex Tester
Test regular expressions with live highlighting, flags, and replacement preview. 100% private, all processing in your browser
Live Highlighting
Matches highlighted as you type
Privacy First
Your data never leaves your device
All Flags
Toggle g, i, m, s, u, y freely
Replace Preview
See replacement result instantly
Frequently Asked Questions
How does the regex tester work?
Enter a pattern, toggle flags, and paste test text. The tool runs the JavaScript RegExp engine locally, highlights every match in place, lists each match with its index and captured groups, and previews any replacement.
Will my data be uploaded to a server?
No. All regex execution is done locally in your browser. Your text and patterns never leave your device, fully protecting your privacy.
Which flags are supported?
The six standard JavaScript flags: g (global), i (ignore case), m (multiline), s (dotAll, dot matches newline), u (unicode), and y (sticky). Toggle any combination.
What are common use cases?
Validate input patterns like emails and phone numbers, build search-and-replace rules, parse logs, extract data from strings, and debug complex expressions step by step.
Is this tool free to use?
Completely free. This is a pure frontend online tool - no registration required, no payment needed, just open and use.
Does it use the same engine as my code?
Yes. The tester uses your browser's native JavaScript RegExp engine, so results match what you will get in Node.js or the browser at runtime.
Related Tools
Base64 Codec
Encode and decode Base64 with UTF-8, URL-safe option, and file-to-Base64. 100% private, all processing in your browser
JSON Formatter
Beautify, minify, and validate JSON data with multiple indent options and key sorting. 100% private, all processing in your browser
Hash Generator
Generate MD5, SHA-1, SHA-256, and SHA-512 hashes from text or files. 100% private, all processing in your browser
Password Generator
Generate strong random passwords with length, charset, and strength control. 100% private, all processing in your browser
URL Encoder
Encode and decode URLs with full-encode mode and UTF-8 support. 100% private, all processing in your browser
UUID Generator
Generate UUID v4 identifiers in batch with uppercase and hyphens options. 100% private, all processing in your browser
Word Counter
Count characters, words, lines, paragraphs, and reading time in real time. 100% private, all processing in your browser
Case Converter
Convert text between seven naming and casing styles at once. 100% private, all processing in your browser
HTML Escape
Escape and unescape HTML entities with a single click. 100% private, all processing in your browser
Lorem Generator
Generate placeholder text by words, sentences, or paragraphs instantly. 100% private, all processing in your browser
Slug Generator
Turn titles into clean, SEO-friendly URL slugs with custom separators and length. 100% private, all processing in your browser