You should activate your Swiss Travel Pass on the very first day you intend to use the Swiss rail, bus, or boat network for a significant journey. In 2026, most Swiss Travel Passes are issued as digital E-Tickets with a pre-selected start date at the time of purchase, meaning they are "auto-activated" for that specific date. However, if you have a "Flex" pass, you must manually select and "activate" each specific travel day on the SBB website or mobile app before boarding your first train of the day. Do not activate a day just for short city tram rides if you can walk, as you want to save your pass days for the expensive long-haul or panoramic routes like the Glacier Express. A common "pro-tip" is to wait until you arrive at the airport (Zurich or Geneva) to set your start date if you haven't done so already, as the pass covers the train ride from the airport to the city center. Once activated, your digital QR code is all you need to show the conductor alongside your passport or ID when they come through the carriage to check tickets.