URL Encoding (also known as Percent Encoding) is a mechanism used to encode special characters in a URL so that they can be safely transmitted over the internet. It ensures that characters that may have special meanings (e.g., spaces, punctuation) or are not allowed in a URL (e.g., non-ASCII characters) are properly encoded.
What is URL Encoding?
URL encoding replaces unsafe ASCII characters with a "%" sign followed by two hexadecimal digits that represent the character's ASCII code. This encoding ensures that the URL can be safely sent over the network.
Why URL Encoding?
Special Characters: Characters like spaces, slashes, question marks, and other symbols have specific meanings in URLs. URL encoding ensures they are treated as part of the data, not as control characters.
Non-ASCII Characters: Characters outside the ASCII range (e.g., Unicode characters) need to be encoded to be safely transmitted.
Reserved Characters: Characters like ?, &, =, # have special meanings in URLs. URL encoding ensures these characters are safely passed in query parameters or as data.
Spaces: In URLs, spaces are not allowed. These are encoded as %20 or + in certain contexts (e.g., in query parameters).
Common Characters and Their URL Encodings:
Character URL Encoding
Space %20
! %21
" %22
# %23
$ %24
% %25
& %26
' %27
( %28
) %29
* %2A
+ %2B
, %2C
/ %2F
: %3A
; %3B
= %3D
? %3F
@ %40
[ %5B
] %5D
Example of URL Encoding:
For the phrase:
nginx
Hello World!
URL encoded version would be:
perl
Hello%20World%21
URL Decoding:
The reverse of URL encoding is URL decoding, where encoded characters (e.g., %20) are converted back to their original form (e.g., space).
How to Encode a URL?
Manually: Replace special characters with their corresponding encoded values.
Programmatically: Many programming languages have built-in functions to perform URL encoding:
JavaScript: encodeURIComponent()
Python: urllib.parse.quote()
PHP: urlencode()
Java: URLEncoder.encode()