Regex Tester — Real-Time Match Highlighting
Enter a regex and test string to see matches and capture groups highlighted in real time.
How It Works
- 1Enter a regex pattern and toggle the flags you need.
- 2Paste a test string — matches and capture groups are highlighted live.
- 3Copy the pattern when it matches what you expect.
About Regex Tester
Regular expressions are one of the most powerful tools in a developer's toolkit, but their terse syntax makes them notoriously tricky to write and debug. This tool provides a real-time testing environment where you enter a regex pattern and a test string, and immediately see all matches highlighted directly in the text. Capture groups are displayed in a clear table showing each group's index, name (for named groups), and matched value — essential for understanding complex patterns with multiple captures. The tool supports all JavaScript regex flags (global, case-insensitive, multiline, dotAll, unicode), each toggleable with a checkbox so you can quickly see how different flags affect your matches. Use it to build and verify patterns for form validation, log parsing, data extraction, search-and-replace operations, and any text processing task. Common patterns include email validation, URL matching, date extraction, and parsing structured log lines. The real-time feedback loop dramatically speeds up regex development compared to running test code repeatedly.
From the blog
Frequently Asked Questions
Which regex flavor does this use?
It uses JavaScript's built-in RegExp engine, which follows the ECMAScript specification. This is the same regex flavor used in Node.js, browsers, and most JavaScript frameworks.
What do the flag buttons mean?
g = global (find all matches), i = case-insensitive, m = multiline (^ and $ match line boundaries), s = dotAll (. matches newlines), u = Unicode.
Can I use named capture groups?
Yes. JavaScript regex supports named groups via (?<name>...). The matched group appears in the results panel labelled with its name, alongside numeric capture groups.
Is my file uploaded to a server?
No. Transmute processes everything locally in your browser using JavaScript and the Canvas API. Your files never leave your device — there is no server, no upload, no cloud processing.
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