data limit

A  data limit  is a restriction on some internet connections (such as free wifi on some trains) that measures how much data you send & receive, caps it at a certain amount, and a good reason to keep page sizes small & use progressive enhancement as a developer, and block unnecessary resources when browsing (such as all trackers & nearly all scripts) as a user.

CZ trains in Germany
Czech trains (with train numbers starting with "EC") have "CDWIFI" SSID with data limits in Germany (500MB in 1st class, 200MB in 2nd class).

Screenshot displaying data used so far:



Screenshot of data limit information for Czech trains: