What are premarket and after-hours trading?
Updated on August 24, 2026 · by Alex
They are the trading sessions outside the exchange's normal hours: premarket happens before the open and after-hours after the close. You can buy and sell, but with far less volume than during the regular session.
The New York Stock Exchange and the Nasdaq trade from 9:30 to 16:00 Eastern time. Premarket runs from 4:00 until the open, and after-hours from the close until 20:00. Every hour quoted around the market is Eastern, so if you follow from another time zone the offset shifts twice a year with daylight saving.
Because that is where the news happens. Companies release their quarterly earnings almost always before the open or after the close, precisely so the market has time to digest them. Same with merger announcements, executive resignations or macroeconomic data.
The result is that a stock can move 10% before the exchange even opens. When you look at the opening price, that reaction has already happened: the move you see as a "gap at the open" is really several hours of off-hours trading.
Treating a premarket price as if it were a normal price. It isn't. In those sessions only a tiny fraction of the usual volume trades, and with little volume the gap between what one person asks and what another offers blows wide open. A premarket price can reflect barely a handful of trades.
The practical consequence: it is very common to see a stock "+7% in premarket" open at +2% and finish the day in the red. The initial off-hours reaction tends to overshoot, and it corrects once real volume comes in.
In the Analysis tab of the site, the PRE and POST labels next to each stock show exactly this off-hours move, so you know whether what you are looking at already happened before the opening bell.
