Why can a stock's price move after the market has closed?

Regular U.S. stock trading runs from 9:30 a.m. to 4 p.m. Eastern Time, but many brokers also offer extended hours: pre-market trading (usually about 7 to 9:30 a.m. ET) and after-hours trading (usually about 4 to 8 p.m. ET). Companies often release big news like earnings outside regular hours, so that's where the first reaction shows up. On Tuesday, Oct 20, Netflix reported its third-quarter results after the close, and Yahoo Finance reported its shares down about 5% in after-hours trading after its fourth-quarter revenue outlook came in below analyst estimates.

Here's the catch for new traders: far fewer people trade in extended hours. With fewer buyers and sellers, prices can swing more, an order might fill only partly or not at all, and the price you get can be worse than during the regular session. Many brokers only accept limit orders then, and each broker sets its own rules. Also, the official closing price is the one set at 4 p.m. After-hours trades don't change it, and the next morning's opening price can land somewhere different again.

So treat an after-hours move as an early, thin first reaction, not the final word. If you see a big jump or drop after the bell, look for the news behind it, and check your broker's extended-hours rules before you ever place an order then. Questions about pre-market, after-hours, or anything else? Ask below, since there are no silly questions here.

Sources: Investor.gov (SEC) glossary on after-hours trading, FINRA's "Extended-Hours Trading: Know the Risks", and Yahoo Finance and CNBC coverage of Netflix's Oct 20, 2026 earnings report.