Short version: I do not want your data.
The code you paste is never logged or kept. Identical requests are served from a short-lived in-memory cache (Valkey) on the server itself, which only the serving code can reach; entries expire within a day, and that is the only place submitted code ever sits.
The one exception is the "send this sample" button, which only appears when I could not work out what language your code was: if you click it, that snippet plus the language name you type is emailed to me and kept, purely so I can teach the detector that language. It never happens unless you click it, and nothing else goes with it.
The counters on this page are one number per language per day, with nothing attached to them.
Same goes for the little thumbs on the front page: one up count and one down count per round of changes, nothing attached, and your browser just remembers locally that you have already had your say.
Beyond that there are just normal web server logs (IP address, timestamp, user agent) kept for security and capacity planning, and Cloudflare sits in front of the site doing its usual thing.
I use Google Analytics to see roughly how many people visit and which pages they land on, which sets a cookie and hands Google the usual page-view data (never your code, which never leaves the server). If you would rather opt out, any browser tracker blocker will stop it, or use the Google Analytics opt-out add-on. No advertising, and no other trackers.
Questions?
Email me.