Temporary Reintroduction of Border Control (Schengen Area)

Although there is generally no internal border control in Schengen Area, it can be temporarily reintroduced. The page lists current border control reintroduction as well as historical data.

Degrees vary. For example, some kind of Germany's border control with Austria started as early as 2015 and is still active to this day. I've seen it in a train from Salzburg to Munich in 2019, but it was like a routine ticket inspection. Just the German police checking passports and visas instead of DB officers checking tickets.