Regex Tester
Test regular expressions with real-time match highlighting
Frequently Asked Questions
What is the regex tester?
A regex tester lets you type a regular expression on one side and paste sample text on the other, with live highlighting of every match, group, and named capture. It is faster than writing throwaway code and ideal for validating complex patterns.
What can I do with it?
Typical tasks: validate user input (phone numbers, email addresses, password rules), extract fields from log lines, perform bulk search-and-replace, write URL routing rules, and parse unstructured text. The UI also shows each capture group so you can see exactly what `$1`, `$2`, etc. will hold.
Which regex dialect is supported?
DevToolkit uses the browser's native JavaScript `RegExp`, identical to what Node.js and frontend code use. Supported flags include `g`, `i`, `m`, `s`, `u`, and `y`. Python, Go, and PCRE have subtle differences (named groups, lookbehind limits), so patterns are not guaranteed to port 1:1.
What are the common pitfalls?
Greedy vs. lazy matching (`.*` vs `.*?`) can over-match; unescaped metacharacters (`.`, `?`, `()`) quietly change meaning; forgetting the `g` flag means only the first match; multi-line text needs `m` and/or `s`. The tester flags invalid patterns in red immediately.
Does my sample text get uploaded?
No. All matching runs in the local JavaScript engine, so sensitive log data or credentials stay on your machine.
How does this compare to regex101?
DevToolkit focuses on the JavaScript dialect with a lightweight, fast UI and integrates with the other tools on the site (JSON, Diff, Base64). For cross-language regex work (PCRE, Python), regex101 is a nice companion — for JS/TS projects, DevToolkit is all you need.