A.62 library(url): Analysing and constructing URL
All Application Manual Name SummaryHelp

Availability::- use_module(library(url)).(can be autoloaded)
Source[det]www_form_encode(+Value, -XWWWFormEncoded)
[det]www_form_encode(-Value, +XWWWFormEncoded)
En/decode to/from application/x-www-form-encoded. Encoding encodes all characters except RFC 3986 unreserved (ASCII alnum (see code_type/2)), and one of "-._~" using percent encoding. Newline is mapped to %OD%OA. When decoding, newlines appear as a single newline (10) character.

Note that a space is encoded as %20 instead of +. Decoding decodes both to a space.

deprecated
Use uri_encoded/3 for new code.