Regular Expressions (Regex) Guide for Beginners — With Examples

Regular expressions (regex) are one of the most powerful text-processing tools available — and one of the most misunderstood. Once you learn the basics, you will use them constantly for validation, search-and-replace, and data extraction.

Basic Syntax

abc        Matches the literal string "abc"
.          Matches any single character (except newline)
d         Matches any digit [0-9]
w         Matches word characters [a-zA-Z0-9_]
s         Matches whitespace (space, tab, newline)
D W S   Uppercase = opposite (non-digit, non-word, non-space)

Quantifiers

*     Zero or more
+     One or more
?     Zero or one (optional)
{3}   Exactly 3
{3,}  3 or more
{3,6} Between 3 and 6

Real-World Examples

Email validation

^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+.[a-zA-Z]{2,}$

Test: user@example.com  ✅
Test: not-an-email      ❌

Indian phone number

^(+91|91|0)?[6-9]d{9}$

Test: +919876543210  ✅
Test: 9876543210     ✅
Test: 1234567890     ❌ (doesn't start with 6-9)

Extract all URLs from text

https?://[^s/$.?#].[^s]*

Matches: https://eazytools.net/blog
Matches: http://example.com/path?q=1

Flags

/pattern/g   Global — find all matches, not just the first
/pattern/i   Case insensitive — "hello" matches "Hello", "HELLO"
/pattern/m   Multiline — ^ and $ match line starts/ends