Percent-encoding

Percent-encoding is a mechanism to encode 8-bit characters that have specific meaning in the context of URLs. It is sometimes called URL encoding. The encoding consists of substitution: A '%' followed by the hexadecimal representation of the ASCII value of the replace character.

Special characters needing encoding are: ':', '/', '?', '#', '[', ']', '@', '!', ' , '&', "'", '(', ')', '*', '+', ',', ';', '=', as well as '%' itself. Other characters don't need to be encoded, though they could.

Depending on the context, the character ' ' is translated to a '+' (like in the percent-encoding version used in an application/x-www-form-urlencoded message), or in '%20' like on URLs.

See also

• Definition of percent-encoding in Wikipedia.
• RFC 3986, section 2.1, where this encoding is defined.
• encodeURI() and encodeURIComponent() — functions to percent-encode URLs