URL Encoding: Why It Matters and How It Works

What is URL Encoding?

URLs can only contain certain ASCII characters. Any other characters must be encoded using percent encoding: a % followed by two hex digits representing the character's byte value.

Reserved vs Unsafe Characters

Reserved characters have special meaning in URLs: / ? # [ ] @ ! $ & ' ( ) * + , ; =

Unsafe characters may be misinterpreted by browsers: space < > { } | \ ^ ~ `

How Encoding Works

Space → %20
& → %26
= → %3D
/ → %2F
? → %3F
# → %23

In JavaScript

// Encode a full URL
encodeURI('https://example.com/path with spaces?q=hello world')
// "https://example.com/path%20with%20spaces?q=hello%20world"

// Encode a URL component (more aggressive)
encodeURIComponent('hello & goodbye')
// "hello%20%26%20goodbye"

// Decode
decodeURIComponent('hello%20world')
// "hello world"

encodeURI vs encodeURIComponent

Function	Encodes	Leaves alone
encodeURI	Unsafe chars	Reserved chars (/ ? # & etc.)
encodeURIComponent	Unsafe + reserved	Letters, digits, - _ . ! ~ * ' ( )

Use our URL Encode/Decode tool for quick conversions.