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Consider the regular expression (x+x+)+y. Before you scream in horror and say this contrived example should be written as xx+y or x{2,}y to match exactly the same without those terribly nested quantifiers: just assume that each “x” represents something more complex, with certain strings being matched by both “x”. See the section on HTML files below for a real example. Let’s see what happens when y

The regular expression I receive the most feedback, not to mention “bug” reports on, is the one you’ll find right on this site’s home page: \b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,}\b. This regular expression, I claim, matches any email address. Most of the feedback I get refutes that claim by showing one email address that this regex doesn’t match. Usually, the “bug” report also includes a suggesti

POSIX bracket expressions are a special kind of character classes. POSIX bracket expressions match one character out of a set of characters, just like regular character classes. They use the same syntax with square brackets. A hyphen creates a range, and a caret at the start negates the bracket expression. One key syntactic difference is that the backslash is NOT a metacharacter in a POSIX bracket

With a few simple regular expressions, you can easily verify whether your customer entered a valid credit card number on your order form. You can even determine the type of credit card being used. Each card issuer has its own range of card numbers, identified by the first 4 digits. You can use a slightly different regular expression to find credit card numbers, or number sequences that might be cr

Introduction The introduction explains how to read the regular expressions reference tables. Quick Reference Use this quick reference if you’ve seen some syntax in somebody else’s regex and you have no idea what feature that syntax is for. Use the full reference tables listed below if you know what feature you want but don’t remember the syntax. Literal Characters, Special Characters, and Non-Prin

Unicode is a character set that aims to define all characters and glyphs from all human languages, living and dead. With more and more software being required to support multiple languages, or even just any language, Unicode has been strongly gaining popularity in recent years. Using different character sets for different languages is simply too cumbersome for programmers and users. Unfortunately,

The regular expressions reference on this website functions both as a reference to all available regex syntax and as a comparison of the features supported by the regular expression flavors discussed in the tutorial. The reference tables pack an incredible amount of information. To get the most out of them, follow this legend to learn how to read them. The tables have six columns for each regular

Feel free to test JavaScript’s RegExp support right here in your browser. Obviously, JavaScript (or Microsoft’s variant JScript) will need to be enabled in your browser for this to work. Since this tester is implemented in JavaScript, it will reflect the features and limitations of your web browser’s JavaScript implementation. If you’re looking for a general-purpose regular expression tester suppo

This quick start gets you up to speed quickly with regular expressions. Obviously, this brief introduction cannot explain everything there is to know about regular expressions. For detailed information, consult the regular expressions tutorial. Each topic in the quick start corresponds with a topic in the tutorial, so you can easily go back and forth between the two. Many applications and programm

Below, you will find many example patterns that you can use for and adapt to your own purposes. Key techniques used in crafting each regex are explained, with links to the corresponding pages in the tutorial where these concepts and techniques are explained in great detail. If you are new to regular expressions, you can take a look at these examples to see what is possible. Regular expressions are

Regular Expressions Tutorial Learn How to Use and Get The Most out of Regular Expressions This tutorial teaches you all you need to know to be able to craft powerful time-saving regular expressions. It starts with the most basic concepts, so that you can follow this tutorial even if you know nothing at all about regular expressions yet. The tutorial doesn’t stop there. It also explains how a regul