Circuit breakers are automatic pauses that halt trading when prices fall too far, too fast. They exist to interrupt panic-driven cascades, give participants time to absorb information, and restore orderly trading - a cooling-off mechanism built into the market's plumbing.

Market-wide levels

For the broad market, circuit breakers trigger at set decline thresholds in the S&P 500 from the prior close. Progressive levels pause trading for a period; a severe enough drop halts trading for the rest of the day. These are rare, blunt tools reserved for genuine crashes - but knowing they exist explains why the tape can simply stop during extreme events.

Single-stock halts

Individual stocks can also be halted - for extreme volatility (limit up/limit down), or pending major news. When a halt lifts, price can reopen far from where it stopped, gapping violently. That reopening gap is a serious risk: a resting stop can fill nowhere near your intended level.

A halt does not remove risk. It stores it up and releases it all at once when trading resumes.

Why it matters for you

Halts and circuit breakers are a reminder that liquidity can vanish exactly when you most want to act. It reinforces the case for defined risk on every position and for not being over-leveraged into known-volatile events like the economic calendar. You cannot manage a position while the market is frozen - so the risk has to be controlled before the freeze.