What after-hours trading is
The main US trading session runs from 9:30 in the morning to 4:00 in the afternoon Eastern time. After-hours trading is the period after the close, and pre-market is the period before the open, when limited trading is still allowed through electronic systems.
These extended sessions exist so that investors can react to news that breaks outside normal hours rather than waiting until the next morning.
Why earnings move prices after hours
Most companies deliberately release earnings either before the market opens or after it closes, to avoid disrupting the regular session. When a big company reports after the close, traders react immediately in the after-hours session, which is why you can see a stock jump or drop 10% at 4:30 in the afternoon.
By the time the regular market opens the next day, the price has often already adjusted to the news. Our Earnings Calendar shows which companies report and whether they are expected before the open or after the close.
The risks of extended hours
Extended-hours trading is riskier than the regular session for a few specific reasons, and beginners should understand them.
- Lower liquidity: far fewer people are trading, so it can be harder to buy or sell at a fair price.
- Wider spreads: the gap between the buy and sell price is usually larger, which costs you more.
- Bigger swings: thin trading means a single order can move the price more than it would during the day.
- Prices can reverse: an after-hours reaction sometimes fades or flips by the next open.
💡 The dramatic move is often not the final one:A stock that spikes or plunges right after earnings can settle very differently once the full market reopens and more buyers and sellers weigh in. The first reaction is not always the lasting one.
How beginners should treat it
For most long-term investors, after-hours trading is something to understand rather than participate in. Watching how a stock reacts to earnings can be informative, but trading in thin, volatile sessions is an easy way to get a worse price.
If you own or follow a company, it is usually enough to note its earnings date, see the reaction, and revisit your view calmly during normal hours.