After-hours / pre-market trading.
In plain English
Regular U.S. stock trading runs from 9:30 a.m. to 4 p.m. Eastern, but many brokers let you trade before and after that in pre-market and after-hours sessions. These extended sessions exist so investors can react to earnings and news released outside market hours. The catch is thin liquidity: far fewer buyers and sellers mean wider bid-ask spreads, jumpier prices, and orders that may not fill at a fair price. A stock can spike or plunge after hours and then open very differently the next morning. Extended-hours trading is riskier and best approached with limit orders.
01Why it matters
Prices in extended hours can swing wildly on thin volume and differ from the next open, so understanding the risks helps you avoid overreacting to an after-hours move.
02The math, step by step
A company reports earnings after the close and its stock jumps 8 percent in after-hours trading on light volume. By the next morning's open, with full participation, the gain settles to 3 percent, so the after-hours price overstated the move.
03What this is NOT
Extended-hours trading is NOT the same as the regular session. Thin volume means wider spreads and sharper swings, so an after-hours price can be misleading and orders may fill poorly.
04Receipts
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