Regular Expression Tester
This tool provides a small, visible test loop for a JavaScript pattern so users can inspect matches before placing the expression into application code.
Test a JavaScript regular expression against sample text
Enter a pattern, optional flags, and sample text. Matches and capture groups are shown below.
Processing mode: browser-only for this tool. The interface does not require a server upload to perform its transformation.
Start with a focused browser tool
This tool provides a small, visible test loop for a JavaScript pattern so users can inspect matches before placing the expression into application code.
Designed for: Developers learning or debugging JavaScript regular expressions.
How to use this tool
Enter the pattern without slash delimiters, choose flags such as i or g, and paste representative sample text. The result lists match text, index positions, and captured groups when the browser accepts the pattern.
How the result is produced
The browser RegExp constructor compiles the supplied pattern. String.matchAll is used for global inspection and a single execution path is used for non-global patterns.
Test examples
Pattern: \b(cat|dog)\b with flag i matches cat or dog as complete words. A pattern such as ^[A-Z]{2}\d{4}$ checks a simple two-letter/four-digit sample format, but it is not a universal identifier validator.
Limitations
Regular expressions are code-like input. A pattern can be computationally expensive or misleading when used on untrusted text. The tester uses JavaScript regex syntax and does not validate patterns for every other programming language.
Privacy and processing
The pattern and sample text are evaluated in the browser. They are not transmitted by this tool.
Related guide
How to test a regular expression without overclaiming what it validates
Related tools in this category
Documentation
- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp
- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/matchAll
This page describes the implementation shipped with the NOFYI Tool Factory. Review the interface output before using it in a production workflow.