key=value&key=value format that web forms and many APIs expect in a request body. Each field becomes a name=value pair, the pairs are joined with &, and any characters that are not safe in a URL are encoded. The only choice is how spaces are written, which differs between two web standards.
Fields
Sample data
Input:
+, and the nested list tags was flattened into tags[0] and tags[1] (with the brackets encoded as %5B and %5D).