The WhatWG URL specification defines an API for manipulating URLs that uses application/x-www-form-urlencoded for parsing and serializing query options.
This API encodes space (octet 0x20) as "+" (octet 0x2B), and consequently decodes "+" (octet 0x2B) as space (octet 0x20).
This is a follow-up to ODATA-1539.