Which one should you actually use?
Compare · Extension vs official export
Most people looking to save their ChatGPT history find a browser extension first. There are hundreds, several are free, and some have hundreds of thousands of installs. They are not a scam and they are not useless — for grabbing a single conversation as a PDF right now, an extension is the faster tool and you should use one.
They solve a different problem than the official export does, and the difference only becomes obvious when it is too late to fix. This page lays out both, including the parts where the extension wins.