For departures from Firenze Santa Maria Novella (SMN), you should aim to arrive at least 20 to 30 minutes before your scheduled departure for high-speed trains (Frecciarossa or Italo). Unlike airports, there is no formal check-in or security screening for domestic Italian rail; however, Florence SMN is a "terminal" station, meaning trains pull in and out from the same side. Platforms 17, 18, and 19 are located quite a long walk from the main concourse (nearly 5-8 minutes), so you need a buffer to find your "Binario" and navigate the crowds. If you still need to purchase or validate a ticket, or if you want to grab a quick espresso at the VyTA bar, give yourself 45 minutes. If you have already checked in via the Trenitalia app and are traveling light, 15 minutes is the absolute minimum, as the boarding gates at the head of the platforms often close their ticket checks 2-3 minutes before the train pulls out.