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.

Character	Encoding
':'	%3A
'/'	%2F
'?'	%3F
'#'	%23
'['	%5B
']'	%5D
'@'	%40
'!'	%21
'$'	%24
'&'	%26
"'"	%27
'('	%28
')'	%29
'*'	%2A
'+'	%2B
','	%2C
';'	%3B
'='	%3D
'%'	%25
' '	%20 or +

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.