100% browser-side · No server · No tracking · No signup — test sensitive text safely
Test your regular expressions without sending a single character to a server. The regex engine runs natively in your browser using JavaScript's built-in RegExp. No account, no network request, no copy of your data kept anywhere.
Open the tester — no signup, no account, nothing stored on any server.
Open the Regex Tester →The tool is a static HTML file served from Cloudflare Pages. It has no backend API, no database, and no analytics that capture input content. Network requests are limited to loading the page itself and the Google Fonts stylesheet.
If your test string contains sensitive data — API keys, emails, passwords, health records — you don't want it sent to a third-party server. Local processing guarantees the data never leaves your machine, even temporarily.
Both Node.js and modern browsers use V8, which implements the same ECMAScript RegExp specification. Patterns that work in the tester will work in Node.js and vice versa (assuming the same engine version and flags).
No. The permalink encodes your pattern, flags, and test string (truncated to 500 chars) into the URL hash (#…). Hash fragments are never sent to the server — they exist only in the browser. Sharing the link with someone shares the URL, not any server-side session.