What is URL encoding ? known also as Percent-encoding


In a URL / Uniform Resource Identifier (URI), you have reserved character that are part of the URL syntax that cannot be used.

For instance:

Percent-encoding, also known as Url Encoding maps (ie encode) :

  • this reserved characters
  • to text that starts with a percent (hence percent encoding)


Url Encoding Set Illustration

Although it is known as URL encoding it is, in fact, used more generally within the main Uniform Resource Identifier (URI) set, which includes both:

It is also used in the preparation of data of the application/x-www-form-urlencoded media type, as is often used in the submission of HTML form data


The purpose detailed is:

  • protecting characters from being interpreted as special/reserved URL delimiters,
  • protecting URLs from being mangled by transmission media with character conversions (like some email systems).


let uri = "sftp://hostname\\foo:Pwd#Pwd@host:port";
console.log("The encoded URI is: "+encodeURI(uri));

The # must normaly be encoded as %23

Reserved Character

Character URL Encoding
! %21
# %23
$ %24
& %26
' %27
( %28
) %29
* %2A
+ %2B
, %2C
/ %2F
: %3A
; %3B
= %3D
? %3F
@ %40
[ %5B
] %5D
Common characters
newline %0A or %0D or %0D%0A
space %20
" %22
% %25
- %2D
. %2E
< %3C
> %3E
\ %5C
^ %5E
_ %5F
` %60
{ %7B
| %7C
} %7D
~ %7E

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