web-encodings.md

application/x-www-form-url-encoded vs Percent-Encoding (RFC-3968: URI encoding)

• Percent-encoding
  • defined in https://www.rfc-editor.org/rfc/rfc3986#page-12
  • called "Percent-Encoding" in the RFC
• application/x-www-form-url-encoded
  • used to send data as part of HTTP requests e.g. in the body of a POST request
    • the encoding in use will be in the Content-Type request header
  • content type HTTP header: application/x-www-form-urlencoded
  • based on an early version of the general URI percent-encoding rules, with a number of modifications such as newline normalization and replacing spaces with + instead of %20.
  • currently defined in the HTML and XForms specifications.
    • In addition, the CGI specification contains rules for how web servers decode data of this type and make it available to applications.
  • is an alternative to multipart/form-data (content type: multipart/form-data; boundary={boundary string})

Differences between them

The encoding used by default is based on an early version of the general URI percent-encoding rules, with a number of modifications such as newline normalization and replacing spaces with + instead of %20.

How to use them in various stacks

Ruby

https://bugs.ruby-lang.org/issues/18822

# percent encode
# ##############
ERB::Util.url_encode(" ") # => "%20"

# percent decode
# ##############
CGI.unescape("%20hello+there") # => " hello there"
# or
# seems to also work?
URI.decode_www_form_component("hi%20there") # => "hi there"


# x-www-form-url-encoded encode
# #############################
CGI.escape(" ") # => "+"
# or
URI.encode_www_form_component(" ") # => "+"

# x-www-form-url-encoded decode
# #############################
URI.decode_www_form_component("+hi%20") # => " hi "
# or
CGI.unescape("%20hello+there") # => " hello there"