Which trains require a reservation?
Most high-speed and overnight trains require an advance reservation. In the Eurail timetable that you receive with your Pass, trains with compulsory reservations are indicated by the symbol R.
Online timetables also indicate when reservation is necessary. In the example below, Eurail Pass holders can board the InterCity from Amsterdam to Brussels without reservation. However, the Thalys from Brussels to Paris is subject to compulsory reservation.

For some trains reservation is not compulsory, but optional if you want to be sure of a good seat. Seat reservation is usually not possible for local or regional trains.
