URL encoding, also known as percent-encoding, is a process of encoding special characters in a URL (Uniform Resource Locator) so they can be safely transmitted over the internet. URL encoding replaces certain characters, such as spaces, with a percent symbol followed by a two-digit hexadecimal representation of the character's ASCII value. The encoded characters are decoded by a URL decoder when a web browser or a server processes the URL. This encoding scheme is necessary because some characters, such as spaces and certain symbols, have a special meaning in URLs and can cause problems if transmitted without encoding. A URL encoder can be implemented as a function or a program in various programming languages to encode strings for use in URLs.