Organizers want people to arrive early and leave extra time for security screening. Every attendee should expect to go through it before entering.
The U.S. Secret Service lists a long run of banned items. Aerosols and spray containers, alcohol, balloons and balls, drones, e-cigarettes, fireworks, firearms and other weapons, glass, and laser lights and pointers all stay outside. Mace and pepper spray are banned too, as are banners, signs, placards, and the structures that support signs. Noisemakers such as air horns, whistles, drums, and bullhorns get the same treatment, along with thermal and metal containers and packages. Security personnel can add anything else they decide poses a risk.
Bags are a gray area. Small clear bags may get through, but entry with a bag is not guaranteed.
For anyone planning to go, the message is simple. Pack light. Organizers advise bringing only essential personal items, leaving prohibited items at home, and following every instruction from event staff and security.
Packing by the list still leaves the final word to security at the door.