# Regex Tester

Canonical: https://dev.eneawork.it/regex
Language: en
Updated: 2026-11-02
Author: Enea Zani (https://eneawork.it)

Test patterns live with flags, groups and replacement.

## What it does

Regular expressions are compact, powerful and easy to get subtly wrong. This tester runs your pattern against a sample as you type, highlights every match, lists capture groups and previews replacements. Flags follow JavaScript RegExp semantics, including lookbehind and named groups.

## How to use

1. Enter the pattern and flags.
2. Paste the test string and inspect highlighted matches.
3. Add a replacement to preview the transformed text.

## FAQ

### Which regex flavor is used?

JavaScript (ECMAScript). Most syntax is shared with PCRE, Java and Python, but lookbehind and Unicode property escapes vary.

### Why do zero-length matches appear?

Patterns such as ^, $ or word boundaries match a position, not characters. The tester advances one character to avoid an infinite loop.

### Is my text sent anywhere?

No. Matching happens in this page.

## Related tools

- [Text Diff](https://dev.eneawork.it/text-diff)
- [Case Converter](https://dev.eneawork.it/case-converter)
- [URL Encoder](https://dev.eneawork.it/url-encoder)

## Machine-readable

- Tool catalogue: https://dev.eneawork.it/tools.json
- Full AI context: https://dev.eneawork.it/llms-full.txt
- Privacy: https://dev.eneawork.it/privacy
- This page in HTML: https://dev.eneawork.it/regex
- Italian version: https://dev.eneawork.it/it/regex