Regular Expression Tester Tool

A Regular Expression (regex) is a mini-language for describing string patterns, used for searching, matching, replacing, and extracting text. It consists of ordinary characters (letters, numbers) and metacharacters (^ $ . * + ? [] () | \), widely used for form validation, log analysis, data cleaning, web scraping, etc. Almost all programming languages have built-in regex engines.

Common regex patterns include: mobile number 1[3-9]\d{9}, email [\w.+-]+@[\w-]+\.[\w.-]+、URL https?://[\w./\-?=&%:#]+, IPv4, ID card, numbers only, Chinese characters [\u4e00-\u9fa5], postal code, QQ number, username, password strength, etc. The "Common Regex Cheat Sheet" in this tool includes these templates; click to use them.

Common reasons: 1) Forgetting the g flag, resulting in only the first match; 2) Unescaped metacharacters, e.g., to match a literal ., write \.; 3) Mixed Chinese/English brackets, spaces, or full-width characters; 4) Improper use of boundary ^ $ with the m multiline flag; 5) Special character rules inside character sets [] differ from outside. Suggestion: remove ^$ for loose matching first, then tighten to locate the issue.

g (global) Global matching, finding all instead of just the first;i (ignoreCase) Ignores case, e.g., /abc/i matches ABC;m (multiline) Multiline mode, making ^ and $ match the start and end of each line;s (dotAll) Allows . to match all characters including newlines. Can be combined, e.g., gim。