Regex Tester & Visualizer
Verify regular expressions in real-time with a visual breakdown. 100% client-side and private — no data ever leaves your browser.
This tool uses a Web Worker to execute regex patterns, preventing "Catastrophic Backtracking" from freezing your browser tab. All processing is local.
This regex tester allows you to verify regular expression patterns against target strings before you deploy them into your codebase. It provides real-time feedback by highlighting matches and offering a visual breakdown of the logic, helping you identify where a pattern is too greedy or failing to capture the intended group.
Reach for this tool when you are debugging complex patterns, learning regex syntax, or validating input masks. It is designed for development and testing, not for executing scripts or processing large datasets. To ensure your data remains private, the tool runs entirely in your browser; no text or patterns are uploaded to a server, meaning it works offline once the page has loaded.
How to Use Regex Tester & Visualizer
- Enter your pattern — Type your regular expression into the regex input field.
- Provide test strings — Paste the text you want to match in the test string area.
- Review matches — Check the highlighted text to see exactly which parts of the string match your pattern.
- Analyze the logic — Use the visualizer breakdown to understand how the regex engine is interpreting your tokens.
Frequently Asked Questions
Is my data sent to a server?
No. All processing happens locally within your web browser using JavaScript. Your regex patterns and test strings never leave your computer, making it safe for testing sensitive internal data.
Does this tool support all regex flavors?
This tool uses the JavaScript regex engine. While most standard patterns are compatible across languages, some specific features of PCRE or Python regex may behave differently here.
What are capturing groups?
Capturing groups are defined by parentheses () in your regex. They allow you to isolate specific portions of a match for later use, which the visualizer will highlight as distinct groups.
How do I handle case-insensitive matches?
You can toggle the case-insensitive flag (i) in the tool settings. This tells the engine to treat uppercase and lowercase letters as identical during the matching process.