How to Encode and Decode URLs: A Complete Developer Guide

URL encoding, officially known as percent-encoding, is a mechanism for encoding information in a Uniform Resource Identifier (URI) under certain circumstances.

Why Do We Need URL Encoding?

URLs can only be sent over the internet using the ASCII character-set. Since URLs often contain characters outside the ASCII set, they must be converted into a valid ASCII format.

URL encoding replaces unsafe ASCII characters with a "%" followed by two hexadecimal digits representing the character's UTF-8 byte value.

Common Encoded Characters:

• Space becomes %20 (or + in some context)
• Exclamation mark ! becomes %21
• Hash # becomes %23
• Dollar $ becomes %24
• Ampersand & becomes %26

URL Decoding

URL decoding is the reverse process of encoding. It replaces percent-encoded sequences like %20 back into their corresponding characters (like spaces).

JavaScript Methods:

• Encoding: encodeURIComponent("hello world!") -> "hello%20world!"
• Decoding: decodeURIComponent("hello%20world!") -> "hello world!"