MWCBMarket-Wide Circuit Breaker Halt
Market-wide circuit breakers stop the entire U.S. equity market rather than a single security. They are keyed to intraday declines in the S&P 500 measured against the prior session's closing value, and are reported with level-specific codes alongside a resumption code. This is the mechanism that halted the whole market repeatedly in March 2020.
What triggers it
- Level 1: the S&P 500 declines 7% from the previous close.
- Level 2: the S&P 500 declines 13% from the previous close.
- Level 3: the S&P 500 declines 20% from the previous close.
How long it lasts
Level 1 and Level 2 each halt trading for 15 minutes, and each triggers at most once per day when reached before 15:25 ET. A Level 3 breach halts trading for the remainder of the session.
How it resumes
After a Level 1 or Level 2 halt, the market reopens following the 15-minute pause. There is no same-day resumption after a Level 3.
What it means for a day trader
Market-wide halts are correlation events. Every position moves together, and hedges that rely on trading during the move are unavailable.
Late-day mechanics differ: a Level 1 or Level 2 decline at or after 15:25 ET does not halt the market, so the last half hour behaves differently from the rest of the session.
Single-stock backtests that include March 2020 without flagging market-wide halts will attribute market-structure outcomes to the strategy.
Related halt codes
Track MWCB halts as they happen
Halt Strategy monitors live NASDAQ and NYSE halts, replays the setup around each event, and backtests outcomes segmented by halt code — so MWCB events are never averaged in with everything else.
Primary sources
Halt Strategy is research software, not investment advice, and does not execute trades. Halt procedures are set by the exchanges and regulators and can change; confirm current rules against the primary sources before acting on them. Read the full disclaimer and editorial policy.