# Regex Tester

Test a regular expression against sample text with live matches.

## URL

https://ilham.dev/tools/regex-tester/

## What It Does

Test a regular expression against sample text and see every match highlighted as you type, with the capture groups listed separately. It uses JavaScript's own regex engine, so what you see here is what you get in a script.

## Features

- Runs in the browser
- No login required

## Input

text input.

## Output

text output.

## Privacy

Processing happens locally in the browser.

No input data is uploaded to ilham.dev.

- Requires login: false
- Requires API key: false
- Stores user data: false


## Examples

- Why does my pattern behave differently in Python or grep?
- Why does .* match more than I expected?




## Questions

### Why does my pattern behave differently in Python or grep?

The dialects differ. JavaScript has no atomic groups or possessive quantifiers, and lookbehind support is comparatively recent. The tool shows which flags it is applying.

### Why does .* match more than I expected?

Greedy quantifiers take as much as they can and then backtrack. Append ? to make it lazy — .*? stops at the first opportunity.