Regex Tester Guide

Quick answer: Test regular expressions against real sample text with live match highlighting before you ship them into code. Open 正则测试 — everything runs locally in your browser, and files never leave your device.

Steps

1. Enter your pattern, e.g. \d{4}-\d{2}-\d{2}.
2. Paste a realistic sample into the text area.
3. Review highlighted matches and captured groups.
4. Toggle global, case-insensitive, and multiline flags as needed.

Important notes

• Test against real data, not hand-crafted clean input — real data is where spaces and full-width characters live.
• Greedy matching is the classic trap: <.*> runs to the last > on the line; use the lazy form <.*?>.
• A correct highlight does not guarantee a correct replace — dry-run replacements on a small scope first.

Common questions

Are regex dialects the same everywhere? Core syntax is portable; lookaheads, named groups, and unicode flags differ between JS, Python, and PCRE — check your target runtime.

A common cheat sheet? Date: \d{4}-\d{2}-\d{2} · Email: [\w.-]+@[\w.-]+.[a-z]{2,} · Chinese chars: [\u4e00-\u9fa5]+