Polymarket US operates nearly 24/7, with a recurring weekly maintenance window every Thursday from 6am–8am ET. Specific markets may have different trading hours based on the underlying event.
All open orders are canceled before maintenance begins. Leaving resting orders on the book during maintenance would expose traders to stale fills when the book reopens.
All API requests return 503 Service Unavailable during maintenance. An explicit rejection is preferable to leaving connections open but non-functional.
Connections are re-enabled first, then markets move from SUSPENDED to OPEN. Order books reopen empty since all orders were cancelled before maintenance. The state change signals that maintenance is complete.
