Investing basics
Pre-market and after-hours trading: how it works and its risks
US stocks trade before the opening bell and after the close, but with fewer buyers and sellers. When the sessions run, why spreads widen, why prices differ between sources, and how Wenlo labels extended-hours prices.
Wenlo EditorialHow we write our guides6 min read
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The trading day has more than one session
Most people think of the US stock market as open from 9:30 a.m. to 4:00 p.m. Eastern Time (ET), Monday to Friday, except holidays. That is the regular session, when almost all trading happens and the official opening and closing prices are set. But trading doesn’t stop completely outside it.
| Session | Usual hours | What to expect |
|---|---|---|
| Pre-market | From as early as 4:00 a.m. to 9:30 a.m. | Light trading, rising toward the open; reactions to overnight news |
| Regular session | 9:30 a.m. to 4:00 p.m. | Most of the day’s volume; the official open and close |
| After hours | 4:00 p.m. to as late as 8:00 p.m. | Light trading; reactions to earnings and news released after the close |
Exactly when you can trade depends on your broker. Some start pre-market trading later than 4:00 a.m. or end after-hours trading before 8:00 p.m., and some now offer overnight trading in selected stocks. On a few days a year, such as the day after Thanksgiving, the regular session closes early at 1:00 p.m. ET, and after-hours trading starts then.
Wenlo’s session badge shows which session it is and what comes next, for example “Pre-market · Opens 9:30 AM ET” or “After hours · Ends 8:00 PM ET”.
How extended-hours trading works
Outside the regular session, orders are matched electronically between buyers and sellers who happen to be trading at the same time. Many of the large firms that keep prices tight during the day trade less or not at all, so there are far fewer orders waiting on each side.
Brokers that offer extended hours usually add rules, such as accepting only limit orders, asking you to mark an order as eligible for extended hours, and not carrying a pre-market order over into the regular session (or the other way round). Stop orders usually trigger only in regular hours. Market, limit and stop orders explains each order type.
Why trade then at all? Companies often release earnings and other big news shortly after 4:00 p.m. or before 9:30 a.m., when most people can’t act on it. Extended hours give investors a chance to react before the next regular session, at the cost of trading in a much thinner market.
The risks: liquidity, spreads and volatility
- Less liquidity. With fewer orders on each side, your order may fill only partly, at a worse price than you hoped, or not at all.
- Wider spreads. The gap between the best bid and the best ask is often much wider than during the day, so the cost of getting in and out is higher.
- Bigger swings. A handful of trades can move the price a long way, especially just after news.
- Prices that don’t hold. An extended-hours price reflects only the people trading then. The next regular session, with far more participants, can open somewhere quite different.
- Competing with professionals. Many of those trading after news are institutions with fast access to information and tools.
Example
An earnings evening
A hypothetical stock closes the regular session at $80.00, with a bid of $80.00 and an ask of $80.02: a two-cent spread. At 4:05 p.m., the company reports disappointing results. By 5:30 p.m., the last after-hours trade is at $72.00, down $8.00 or 10.0% from the close, on a few thousand shares, and the quote is $71.60 bid and $72.40 ask: an 80-cent spread, forty times wider.
The next morning, after more investors have read the report, the stock opens at $75.00. Someone who sold at $72.00 the evening before got $3.00 a share less than the open; someone who bought then is $3.00 ahead. Neither outcome was knowable at 5:30 p.m.
Risk
Use limit orders and smaller sizes
In thin markets, a limit order is what stands between you and a fill far from the last price. Even with one, the price you set may look very different the next morning. An extended-hours move is a first reaction, not the market’s settled view.
Why prices differ between sources
Outside regular hours, it is common to see two websites or apps show different prices for the same stock at the same moment. Usually none of them is wrong. They are answering slightly different questions:
- Which price is the headline. Some sources replace the main price with the latest extended-hours trade; others keep the regular-session close as the main price and show the extended price separately.
- Which trades count. Some show trades from every venue; others show only certain exchanges or trading systems, which can differ by a few cents or more when trading is thin.
- What the change is measured from. Most measure the extended-hours change from the regular session’s close; others compare it with the last trade of any session.
- How fresh it is. Some sources are real-time, others are delayed or refresh every few minutes. In a quiet session, the “latest” price can be an hour old.
The official closing price is set at the end of the regular session by the exchange where the stock is listed. It is the reference most sites use for the next day’s change, which is why after-hours trades don’t change “today’s close”.
How Wenlo shows extended-hours prices
When Wenlo has a pre-market or after-hours price for a stock, it keeps the regular session’s price as the main price and shows the extended one on its own line, so the two are never mixed up:
- On a ticker page, the extended price appears under the main price in purple, labeled “Pre-market” or “After hours”, with its change and its own time, for example “After hours $249.07 +0.45 (+0.18%) · 5:42 PM ET”. Its change is measured from the regular close.
- Watchlists show the same price as a small line under each row’s price (“PM” or “AH” on phones).
- On the 1D and 5D charts, pre-market and after-hours bars sit on a light shaded band, with a key under the chart.
- Every price carries an “as of” time. Prices marked LIVE are real-time trades from select US venues, not the consolidated market price.
Because these prices come from a thinner market, treat them as an early read on how the next session might start. Before you trade, check the live quote in your brokerage account, which shows the bid, ask and sizes your order will actually meet.
Key takeaways
- The regular session is 9:30 a.m. to 4:00 p.m. ET. Pre-market and after-hours sessions run on either side, with hours that vary by broker.
- Thin trading means wide spreads and big swings. Prices can move far on a few trades.
- Limit orders are the norm, and often the only kind accepted.
- Extended-hours prices are provisional. The next open can be very different.
- Different sources can disagree about which price to show and what to measure it from; check the label and the time.
Extended hours make it possible to react to news quickly, but they are a harder place to trade. Knowing the rules and the risks helps you read an evening price move for what it is: an early, incomplete signal.
Try it with real numbers
Open a ticker page after 4:00 p.m. ET or before 9:30 a.m. ET and look for the extended-hours line under the price, then switch the chart to 1D to see the shaded sessions.