# Regex Tester

> Test and debug regular expressions with live matches, capture groups, and highlighted results.

URL: https://uttir.com/regex-tester
Categories: developer-tools, text-tools
Privacy: Your pattern and test text are processed entirely in your browser and never uploaded.

## About

Regular expressions are powerful but easy to get wrong. This tester shows you exactly what your pattern matches as you type, highlighting every match in your test text and listing capture groups so you can verify the pattern before you ship it.

Everything runs locally with the browser’s native regex engine, so patterns and sample data never leave the page — fine for testing against real user data, logs, or anything sensitive.

## How to use

1. **Type your pattern** — For example: \b\w+@\w+\.\w+ to match email addresses.
2. **Toggle flags** — Case-insensitive, multiline, dot-all, Unicode, and sticky modes.
3. **Enter test text** — Every match is highlighted and listed with its capture groups.

## Examples

### Find email addresses

A simple pattern that finds email-like strings in a block of text.

Input:

```
\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,}\b
```

Output:

```
All email addresses in the test text, highlighted with capture groups shown.
```

## FAQ

### Which regex syntax is supported?

JavaScript’s ECMAScript regular expression syntax, which is what runs natively in your browser.

### Why do I need the “global” behavior?

The tester always finds every match in your text so you can review them all. The flag buttons control the other behaviors.

### What do the capture groups mean?

Groups are the parts of the match captured by parentheses in your pattern. They are shown per match so you can confirm they capture the pieces you expect.

## Related tools

- [JSON Formatter](https://uttir.com/json-formatter) — Format, beautify, and validate JSON with adjustable indentation — instantly in your browser.
- [Text Diff](https://uttir.com/text-diff) — Compare two texts line by line and see exactly what was added, removed, or kept.
- [Base64 Decoder](https://uttir.com/base64-decoder) — Decode Base64 back into readable text, with clear errors for malformed input.

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For the full HTML page with the live tool, visit https://uttir.com/regex-tester.
This file is the markdown rendering at https://uttir.com/regex-tester.md. See https://uttir.com/llms.txt for a site-wide summary.