This free online regex tester runs 100% client-side inside your browser tab using your device's native ECMAScript RegExp engine. No regex pattern, test string, or replacement data is ever sent to any remote server, guaranteeing zero latency, zero telemetry, and complete privacy for proprietary code and sensitive data.

All standard ECMAScript regular expression flags are supported with interactive toggle pills: g (global match across the entire string), i (case-insensitive matching), m (multiline mode where ^ and $ match line boundaries), s (dotAll mode allowing . to match newlines), u (unicode mode with code point escapes), and y (sticky match at lastIndex).

Our built-in pattern explanation engine analyzes your regular expression in real time, decomposing character classes (\d, \w, \s), quantifiers (*, +, ?), anchors (^, $), capturing groups, lookaheads, lookbehinds, and named groups into clear human-readable explanations.

Yes! Use the Code Snippets studio tab or press Alt+S to generate production-ready code across 10 programming languages: JavaScript/TypeScript, Python, Go, Java, C#, Rust, PHP, Ruby, Swift, and Bash/ripgrep.

Enter your replacement pattern in the Replace studio tab. Use $1, $2 to reference numbered capturing groups, $& for the entire matched string, or $` and $' for prefix/suffix substrings. The tool displays a live preview of all substitution results in real time with 1-click copy and file download actions.

Catastrophic Backtracking (ReDoS) occurs when a regular expression contains nested or overlapping quantifiers (such as (a+)+ or (a|a)+) evaluating non-matching input strings, causing exponential comparison steps (O(2^n)). The tester includes an automated ReDoS heuristic detector to warn you when hazardous nested quantifier structures are entered.

Yes. The Unit Tests tab lets you create, run, and persist test cases with expected match outcomes (Expect Match vs Expect No Match) in your browser's localStorage. The suite continuously evaluates all test cases in real time, reporting pass/fail status and summary metrics.

You can copy all matched strings, export a formatted plain text file (.txt), download an RFC-4180 compliant CSV table (.csv), download a complete GitHub-flavored Markdown audit report file (.md) with Line:Column positions and token explanations, or export a structured JSON audit report (.json) for CI/CD documentation.

Clicking the '🛡️ Escape Regex' button automatically escapes all special characters (such as ., *, +, ?, ^, $, (, ), [, ], {, }, |, and \) with backslashes. This converts arbitrary user strings into safe literal patterns that match exact characters without triggering regex syntax errors.

Press Alt+P for DevToys Smart Clipboard Auto-Detect (reading regexes, constructors, Python code, and flags directly from clipboard), / to instantly focus the pattern input, Esc to dismiss modal dialogs or clear the workspace, Alt+K or ? to open the Keyboard Shortcuts modal, Alt+S to view Developer Code Snippets and download standalone scripts, Alt+D to star/bookmark the tool, Alt+M to download the Markdown audit report, Alt+V to toggle between 2-Column Split Studio and Stacked views, Alt+R to load a random preset ('Surprise Me'), Alt+C to copy all matches, and Ctrl+Enter to copy matches immediately.