Yes, you still need a physical or digital seat reservation ticket to board most Shinkansen if you are using a Japan Rail Pass in 2026. While the JR Pass itself acts as your "base fare," you must obtain a seat assignment at a ticket machine or a "Midori-no-Madoguchi" service counter. For the Nozomi and Mizuho (the fastest trains), JR Pass holders must now pay an additional supplement fee to use them, which was a major rule change implemented in late 2023. For other trains like the Hikari or Kodama, seat reservations are free for pass holders but highly recommended, especially during peak travel seasons like Golden Week or Obon. Some trains, such as the Hayabusa on the Tohoku line, are "Reserved Only," meaning you cannot board at all without a specific seat ticket. If you have the new "digital" JR Pass, you can conveniently make these reservations through the official JR reservation website before even arriving at the station.