Regex Cheat Sheet: Common Patterns Every Developer Needs

Regular expressions have a reputation for being unreadable, and honestly, some are. But a small set of patterns covers the vast majority of real-world use — validating input, extracting data, cleaning text. Here's the practical set.

Email address (good-enough version)

\b[\w.-]+@[\w.-]+\.\w+\b

This won't catch every technically-valid email per the RFC spec (nothing simple does), but it correctly matches the overwhelming majority of real addresses people actually use.

URL

https?:\/\/[^\s]+

Matches http:// or https:// followed by any non-whitespace characters. Good for pulling links out of pasted text.

Digits only

^\d+$

The ^ and $ anchors mean the entire string must be digits, not just contain some — useful for validating a form field is purely numeric.

Whitespace cleanup

\s+

Matches one or more whitespace characters (spaces, tabs, newlines) in a row — pair with a replace-with-single-space operation to clean up messy pasted text.

Extracting hashtags or mentions

[#@]\w+

Matches a # or @ followed by word characters — grabs hashtags and @mentions out of social text in one pattern.

The three flags worth knowing

• g (global) — find all matches, not just the first one
• i (case-insensitive) — treat A-Z and a-z as equivalent
• m (multiline) — makes ^ and $ match the start/end of each line, not just the whole string

The fastest way to get a pattern right isn't memorizing syntax — it's testing against real sample text and watching what actually matches, adjusting until it's correct.