What Is After-Hours Trading? How Premarket and Extended-Hours Stock Trading Work, and the Risks to Know

Big stock moves often happen while the main market is closed. Understanding how those sessions work can help you read the headlines, and avoid costly surprises if you ever trade in them.

What is after-hours trading?

After-hours trading is buying and selling stocks after the regular session ends at 4 p.m. Eastern time. Premarket trading happens before the 9:30 a.m. open. Together they are called extended-hours trading. Prices can move sharply in these sessions, often on earnings news, but fewer buyers and sellers make trading riskier.

The Securities and Exchange Commission's investor site, Investor.gov, defines extended-hours trading simply as trading that happens outside regular hours. For stocks listed on U.S. exchanges, those regular hours run from 9:30 a.m. to 4 p.m. Eastern, Monday through Friday. Everything before or after that window is "extended."

When you see a headline saying a stock "jumped 12% after hours," it means the share price traded in that evening session was 12% above the 4 p.m. closing price. That move is real, but it is based on far less trading than a normal day, and it may look different by the next morning.

What are the trading hours for U.S. stocks?

Today, U.S. stock trading runs in three main pieces, all in Eastern time:

• Premarket: 4 a.m. to 9:30 a.m. on Nasdaq.
• Regular session: 9:30 a.m. to 4 p.m., starting with an opening auction and ending with a closing auction.
• After hours: 4 p.m. to 8 p.m. on Nasdaq.

Those times come from Nasdaq's trading-hours page. NYSE Arca, the New York Stock Exchange's electronic market that lists many exchange-traded funds, runs similar "early" and "late" sessions from 4 a.m. to 9:30 a.m. and 4 p.m. to 8 p.m., according to a Jones Day analysis. Your broker may offer a shorter window than the exchanges do, so the hours you can actually trade depend on the firm you use.

Most of the action still happens during the regular session. Nasdaq CEO Adena Friedman said in April that only about 2% of total volume takes place outside the current 4 a.m. to 8 p.m. day, Markets Media reported.

Why do stocks move so much after the closing bell?

The main reason is news. Many companies release quarterly earnings or other major updates just after 4 p.m. so investors have time to digest them before the next regular session. Those after-hours sessions are when the first reaction shows up.

October 20, 2026, offered several examples. Super Micro Computer released a preliminary sales update at 4:30 p.m. Eastern, and its stock rose about 11% to 16% after hours. The same evening, shares of Netflix fell after its results, which we covered in our look at Netflix's Q3 earnings and its ad revenue forecast cut, and Intuitive Surgical dropped about 7%, as we explained in our story on why a narrower forecast spooked Intuitive Surgical investors.