Debug Regular Expressions Visually
Regular Expressions (Regex) are an incredibly powerful way to search and manipulate text, but their syntax looks like absolute gibberish when an error occurs. Our Online Regex Tester provides real-time visual highlighting and debugging so you can see exactly what your pattern is matching.
Essential for Text Parsing
Whether you are scraping a website, validating user input, or parsing server logs, Regex is the tool for the job. Use our debugger to test common patterns:
- Input Validation: Ensure a user's input strictly matches the format of an email address, phone number, or ZIP code before submitting a form.
- Data Extraction: Isolate and extract specific data points (like IP addresses or error codes) from massive, unstructured text logs.
- Capture Groups: Visually test your
(capture groups)to ensure you are extracting the exact substring needed for your backend logic.
How to Use This Tool
- Upload or Input Data: Select your file or paste your data directly into the tool interface. Everything remains on your device.
- Configure & Process: Adjust any optional settings if necessary. The tool will process your data instantly inside your browser.
- Download Result: Preview the output and click the download or copy button to save your final results.
Frequently Asked Questions
Which regex flavor does this tool use?
The tool primarily utilizes the JavaScript (ECMAScript) regex engine, as it runs natively in the browser. It supports modern features like lookaheads and named capture groups.
What are the flags (g, i, m)?
`g` (Global) finds all matches rather than stopping at the first. `i` (Case-Insensitive) ignores capitalization. `m` (Multiline) changes how the `^` and `$` anchors behave across line breaks.
Why is my regex hanging the browser?
You have likely encountered 'Catastrophic Backtracking'. This occurs when a complex pattern with nested quantifiers (like `(a+)+`) fails to match, causing the engine to try millions of permutations.