Glossary
Query string
The part of a URL after the question mark, carrying key and value pairs that travel with the request.
It is where UTM parameters live, which is why they survive when the referrer does not: the query string is part of the URL and goes wherever the URL goes, including into a chat message or a printed QR code.
It is also visible to everyone in the chain, so it is the wrong place for anything private. An identifier in a query string ends up in server logs, in browser history and in the referrer sent onwards.
Order does not matter to a server reading parameters, but it does to anything comparing URLs as strings, including some caches and most analytics tools.
