Regular Expressions for Beginners: Learn Regex with Examples

What Are Regular Expressions?

Regular expressions (regex) are patterns that describe text. They're used for searching, matching, and manipulating strings in virtually every programming language.

Basic Building Blocks

Pattern	Matches	Example
.	Any character	c.t → cat, cut, c9t
\d	Any digit	\d\d → 42, 99, 01
\w	Word character	\w+ → hello, abc123
\s	Whitespace	\s → space, tab, newline
^	Start of string	^Hello → "Hello world"
$	End of string	world$ → "Hello world"

### Quantifiers

Pattern	Meaning	Example
	0 or more	abc → ac, abc, abbc
+	1 or more	ab+c → abc, abbc
?	0 or 1	colou?r → color, colour
{3}	Exactly 3	\d{3} → 123, 456
{2,4}	Between 2 and 4	\d{2,4} → 12, 123, 1234

### Practical Examples Email validation:

^[\w.-]+@[\w.-]+\.\w{2,}$

Phone number (US):

^\(?\d{3}\)?[-.\s]?\d{3}[-.\s]?\d{4}$

URL:

https?://[\w.-]+(/[\w.-])

Hex color code:

^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$

Groups and Alternatives

• (abc) — capturing group
• (?:abc) — non-capturing group
• a|b — matches a OR b
• [abc] — character class: a, b, or c
• [^abc] — NOT a, b, or c
• [a-z] — range: any lowercase letter

Testing Your Regex

The Regex Tester tool lets you:

• Write regex patterns with instant feedback
• See all matches highlighted in your test text
• Understand what each part of your pattern does
• Test edge cases before using in production

Common Mistakes

Forgetting to escape special characters — ., *, ?, (, ) have special meaning

Greedy matching — . grabs as much as possible; use .? for lazy matching

Not anchoring patterns — without ^ and $, patterns match anywhere in the string

Over-complex patterns — if your regex is unreadable, split it into multiple simpler checks