URL encoding, also known as percent-encoding, is a method used to convert characters that are not allowed in URLs into a format that can be transmitted over the Internet. It replaces unsafe ASCII characters with a “%” symbol followed by two hexadecimal digits representing the character’s ASCII code.

URLs are designed to use a limited set of characters from the ASCII character set. However, many characters commonly used in text, such as spaces, ampersands, and non-ASCII characters, are not allowed in URLs. URL encoding provides a way to represent these characters in a URL-safe format.

The encoding process works by replacing unsafe characters with a percent sign (%) followed by two hexadecimal digits. For example, a space character is encoded as “%20”, while the ampersand (&) becomes “%26”. Characters that are already safe to use in URLs, such as letters, numbers, and certain symbols like hyphens and underscores, remain unchanged.

URL encoding is crucial for several reasons:

  1. Ensuring proper transmission of data: It prevents special characters from being misinterpreted by servers or browsers.
  2. Maintaining data integrity: It ensures that the original information can be accurately reconstructed from the encoded URL.
  3. Handling non-ASCII characters: It allows for the representation of characters from various languages and character sets in URLs.

Common use cases for URL encoding include:

  • Encoding form data submitted via GET requests
  • Creating query string parameters in URLs
  • Encoding special characters in file names or paths
  • Handling internationalized domain names (IDNs)

Many programming languages and web frameworks provide built-in functions or libraries for URL encoding and decoding. These tools make it easy for developers to implement URL encoding in their applications, ensuring that data is properly formatted for transmission over the web.