cookies
What 'clear browsing data' leaves behind
I filled a Chrome profile with two test sites, then pressed Delete browsing data exactly as the dialog opened. One site was wiped. The other was not touched.
What incognito mode actually hides, and from whom
I opened one site in a normal Chrome window and an incognito one and compared what it saw. 26 of 29 things matched. Here is what incognito changes.
What 'Reject all' on a cookie banner actually does
I clicked reject all on a real news site and measured what changed. On a good banner it does stop the trackers. Here is the part it does not touch.