Text Diff Checker
Text Local only
Regex Tester, Debugger & Visualizer
Local onlyTest, explain, visualize, secure, and benchmark regular expressions locally.
Regex 1
/
Regular expression
Enter a pattern, or paste a JavaScript regex literal with flags
Enter a pattern and test text to begin
Worker-isolated, local only
Test text · 0 lines
Type, paste, drop, or import text to test…
How to use it
- 01
Enter a pattern and text
Use raw ECMAScript syntax or paste a JavaScript literal, then add text manually or import a local document.
- 02
Inspect every behavior
Navigate matches and groups, preview replacements, run tests, inspect the AST, and generate a syntax diagram.
- 03
Check safety and portability
Run bounded ReDoS analysis, compare Native and RE2 behavior, benchmark safely, and generate code for eight languages.
Frequently asked questions
Are my patterns, test text, or files uploaded?
No. Evaluation, imports, visualization, tests, and analysis all run locally in your browser.
Which regex engines are supported?
Native mode follows your browser's ECMAScript RegExp implementation. RE2 Safe mode uses a linear-time engine and intentionally rejects unsupported backtracking features.
Why can a dangerous regex time out?
Some native expressions can trigger catastrophic backtracking. Nobuf runs untrusted evaluation in a disposable Worker and terminates it when the time limit is reached.
What is the difference between Native and RE2?
Native supports the full JavaScript feature set, including lookaround and backreferences. RE2 prioritizes predictable linear-time execution and omits features that require backtracking.
Related tools
Keep working with other private browser utilities.