What is URL encoding and why is it necessary?

• URL encoding replaces non US-ASCII characters with escaped sequences that ensure the URL is valid.
• Escaped sequence start with a % and are followed by a two-digit hexadecimal code. The @ character is encoded as %40.
• Servers and Internet browsers may reject invlaid URLs or URLs that are consindered unsafe.
• URL encoding is also referred to as percent-encoding.

What is URL decoding?

• URL decoding restores escaped sequences back into the original unencoded character.
• A server script or web page may need to restore the original unencoded characters for use in data processing or to display to a human visitor.
• Make sure to properly encode any HTML entities in the decoded URL before displaying them on a web page.
• Encoding and decoding HTML entites is a different topic, but yes, it's a thing too.