Circuit Breaker

US market-wide circuit breakers track the S&P 500's drop from the previous close: a 7% or 13% decline halts trading for 15 minutes (these two levels do not halt trading at or after 3:25 p.m. New York time), and a 20% decline closes trading for the rest of the day. Individual stocks also have a separate mechanism that briefly pauses trading in that stock after an extreme move over a short period.