URL encoding, also known as percent encoding, is a mechanism to convert characters into a format that can be transmitted over the Internet. URLs can only be sent over the Internet using the ASCII character set. Since URLs often contain characters outside the ASCII set, they need to be converted into a valid ASCII format.

Key Principles of URL Encoding

URL encoding replaces unsafe ASCII characters with a "%" followed by two hexadecimal digits. For example, a space is encoded as %20 or sometimes as a plus (+) sign¹. This ensures that the URL can be correctly interpreted by web browsers and servers.

Reserved Characters

Certain characters have special meanings in URLs and must be encoded to avoid confusion. These include characters like the dollar sign ($), ampersand (&), plus (+), comma (,), forward slash (/), colon (:), semi-colon (;), equals sign (=), question mark (?), and the "at" symbol (@). For example, the dollar sign is encoded as %24².

Unsafe Characters