Track 01 · Market Foundations
Orders, spreads and liquidity
Market orders, limit orders, the bid-ask spread, and what volume is actually telling you.
Most of the day’s volume — and the tightest spreads — happen inside the regular session. Outside it, everything gets thinner.
- 04:00–09:30Pre-marketFew participants, wide spreads, small size.
- 09:30Opening auctionThe opening price is matched in one batch.
- 09:30–16:00Regular sessionThe tightest quotes and most of the volume.
- 16:00Closing auctionThe official closing price is set.
- 16:00–20:00After-hoursThin again: wider spreads, smaller size.
- 04:00–09:30Pre-marketFew participants, wide spreads, small size.
- 09:30Opening auctionThe opening price is matched in one batch.
- 09:30–16:00Regular sessionThe tightest quotes and most of the volume.
- 16:00Closing auctionThe official closing price is set.
- 16:00–20:00After-hoursThin again: wider spreads, smaller size.
Market order vs limit order
A market order executes immediately at the best available price: certain to fill, but the price is not guaranteed. A limit order only fills at your price or better, so the price is guaranteed but the fill is not.
For a liquid large-cap the two are nearly interchangeable. For a thinly traded stock, a market order can move several percent worse than the quote you were looking at.
The bid-ask spread
The bid is what buyers are offering; the ask is what sellers want. The gap between them is the spread, an immediate, invisible cost you pay on every round trip.
Spreads are widest when a stock is least liquid, which is why a “cheap” small cap can be up to date on the chart and still cost you more to trade than a large-cap with a tighter spread.
Volume and liquidity
Volume is the number of shares traded in a period. High volume means many participants, tight spreads and orders that fill near the price you saw. Low volume means the opposite.
A price move on heavy volume carries more information than the same move on a quiet day: more money actually agreed at the new price.
- Volume above the 20-day average: conviction behind the move.
- A big move on falling volume: often one large participant rather than a consensus.
- Average daily volume is the practical cap on how large a position you can build or exit.
When the US market is open
Regular trading on the NYSE and Nasdaq runs 9:30 a.m. to 4:00 p.m. Eastern, Monday to Friday. Pre-market and after-hours sessions exist either side of it, with far fewer participants and wider spreads.
Most of the day’s volume, along with the tightest pricing, occurs inside the regular session, which is why intraday charts look so different before the open.
Three things to remember
- 01A market order guarantees execution; a limit order guarantees price.
- 02The spread is a real cost; liquidity decides how large it is.
- 03Volume tells you how many participants agreed with a price move.
Try it on live data
Tools on this site are for research and education. Nothing here is financial advice or a recommendation to buy or sell.