regex101: build, test, and debug regex
Regular expression tester with syntax highlighting, explanation, cheat sheet for PHP/PCRE, Python, GO, JavaScript, Java, C#/.NET, Rust.
RegExr: Learn, Build, & Test RegEx
Menu RegExr is an online tool to learn, build, & test Regular Expressions (RegEx / RegExp). Supports JavaScript & PHP/PCRE RegEx. Results update in real-time as you type. Roll over a match or …
Regular expression - Wikipedia
For example, by defining a character style that makes text into small caps and then using the regex [A-Z]{4,} to apply that style, any word of four or more consecutive capital letters will be automatically …
RegEx for matching "A-Z, a-z, 0-9, _" and "." - Stack Overflow
May 14, 2019 · I need a regex which will allow only A-Z, a-z, 0-9, the _ character, and dot (.) in the input. I tried: [A-Za-z0-9_.] But, it did not work. How can I fix it?
Regular expression syntax cheat sheet - JavaScript | MDN
Jan 8, 2026 · Non-word character class escape: Matches any character that is not a word character from the basic Latin alphabet. Equivalent to [^A-Za-z0-9_]. For example, /\W/ or /[^A-Za-z0-9_]/ matches …
RegEX Cheat Sheet & Quick Reference
A quick reference for regular expressions (regex), including symbols, ranges, grouping, assertions and some sa
Regex Cheat Sheet
If you are a complete beginner, you should get a firm grasp of basic regex syntax just by reading the examples in the tables. I tried to introduce features in a logical order and to keep out oddities that I've …
Regex Tutorial - How to write Regular Expressions
Dec 22, 2025 · A regular expression (regex) is a sequence of characters that defines a search pattern. It is mainly used for pattern matching in strings, such as finding, replacing, or validating text. Regex is …
SimpleRegex - Free Online Regex Tester & Pattern Generator
Free online regex tool for developers with syntax highlighting, pre-built examples, and instant match results. No installation required.
Regex Cheatsheet - Complete Regular Expression Reference | RegexBox
Comprehensive regex cheatsheet with syntax reference, character classes, quantifiers, anchors, and common patterns. Quick reference guide for regular expressions with examples and explanations.