Percentenkoodattu

Percentenkoodattu, also known as percentage encoding or percent-encoding, is a method used in computing and telecommunications to encode information in a Uniform Resource Identifier (URI), which includes both Uniform Resource Locators (URLs) and Uniform Resource Names (URNs). This encoding process converts special characters and reserved characters into a percent sign (%) followed by two hexadecimal digits representing the ASCII code of the character. The primary purpose of percent-encoding is to ensure that data can be transmitted reliably over networks without ambiguity or unintended interpretation by servers or clients.

Percent-encoding is defined in standards such as RFC 3986, which outlines the rules for URI syntax. Characters that are not alphanumeric (letters A-Z, a-z, and digits 0-9) and are not part of the reserved set (such as :, /, ?, =, &, etc.) must be encoded if they appear in a component of the URI where they could cause confusion. For example, spaces are encoded as %20, and symbols like @ are encoded as %40. Reserved characters, however, are only encoded if they appear in contexts where they have a different meaning, such as within a query string.

Percent-encoding is widely used in web development, particularly when constructing URLs dynamically or when dealing with user input that may contain unpredictable characters. It ensures compatibility across different systems and prevents issues like malformed URLs or security vulnerabilities, such as cross-site scripting (XSS) attacks, when improperly handled. Tools and libraries in programming languages often provide built-in functions to perform percent-encoding automatically, simplifying the process for developers.