What is a regex tester online?

A regex tester online (regular expression tester) lets you write a pattern and test it against any text in real time, showing live match highlights and capture groups — right in your browser.

Is this regex tester free for beginners?

Yes! ZeroApiTools' Regex Tester is 100% free with no signup. It's designed for beginners with live highlighting and flag toggles, but powerful enough for experienced developers.

Is my test data uploaded to a server?

No. Everything runs entirely in your browser. Your regex patterns and test strings are never sent anywhere.

Regex Tester — Free Online Tool (2026)

Use Regex Tester for free — test regular expressions with live match highlighting. This tool runs 100% in your browser with zero server uploads. Part of ZeroApiTools, a collection of 65+ free developer tools. No signup, no API keys, no data collection. Works offline.

The free Regex Tester Online on ZeroApiTools lets you write, test, and debug regular expressions in real-time with live match highlighting — no signup, no server upload required. Whether you're a beginner learning regex patterns or an experienced developer validating complex input, this regular expression tester works entirely in your browser.

What is a Regex Tester?

A Regex Tester (Regular Expression Tester) is a tool that lets you apply a regex pattern to a block of text and instantly see which parts of the text match. It shows capture groups, match positions, and works with all standard flags like `/g` (global), `/i` (case-insensitive), and `/m` (multiline).

How to Use the Regex Tester on ZeroApiTools?

Type or paste your regular expression pattern into the Pattern input box (e.g., `\\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\\.[A-Z]{2,}\\b`).
Select your regex flags (g, i, m) as needed from the checkboxes.
Paste your test string or block of text into the main editor — matches are highlighted instantly as you type.

Is this regex tester free to use?

Yes. This is a fully free regex tester online — no account, no limits, and no data is uploaded anywhere. Your patterns and test strings stay in your browser.

What regex engine does this tester use?

This regex tester uses JavaScript's built-in `RegExp` engine, making it ideal for testing patterns intended for JavaScript, Node.js, and browser-side validation code.