Introduction

Normally, URLs are comprised of the so-called safe characters which include the lower- and uppercase alphanumerics a-zA-Z and the digits 0 through 9 as well as the characters: dollar-sign ($), hyphen (-), underscore (_), period (.), plus sign (+), exclamation point (!), asterisk (*), apostrophe ('), left parenthesis ((), and right parenthesis ()).

URL Encoding

Any other characters are considered unsafe either due to their reserved meaning or because they are outside the ASCII range. Any such characters must be URL-encoded. This is achieved by representing each unsafe character via a % symbol followed by a hexadecimal sequence of digits which uniquely identifies it:

Whenever the above sequences are encountered in a URL, they are interpreted as the literal character they represent.