Module 1 · The Order Book
The DOM / Price Ladder
Resting bids and offers around a central price column.
In this lesson you'll
- Read the anatomy of a DOM ladder
- Identify best bid, best ask and the spread
- Understand depth levels
The ladder is built around a central price column. Resting buy limit orders (bids) sit below the current price; resting sell limit orders (asks/offers) sit above it. Each price shows a size — the total contracts resting there.
- Best bid = the highest price a buyer will pay (top of the bid stack).
- Best ask (offer) = the lowest price a seller will accept (bottom of the ask stack).
- Spread = best ask − best bid. In liquid futures (e.g., ES) it's usually one tick; a wider spread means thinner liquidity.
Key takeaways
- The DOM shows resting limit orders: bids below price, asks above.
- Best bid = highest bid; best ask = lowest offer; spread = the gap between them.
- Bar/size = contracts resting at that price; depth = levels beyond the inside.
- Resting orders are intentions that can be cancelled — not commitments.
Check your understanding
Pick an answer to reveal instant feedback. Answer every question to complete the lesson.
Why that's off: The best offer is the LOWEST ask, not the highest.
Why that's off: Most-traded is the POC (executed volume), not a resting-order term.
Why that's off: The close is unrelated to resting depth.
The best ask (best offer) is the lowest resting sell price — the cheapest you can buy immediately. The best bid is the highest resting buy price.
Why that's off: Executed trades are the footprint/tape, not the DOM.
Why that's off: Volume profile is executed volume per price.
Why that's off: Candles show OHLC price.
The DOM shows resting limit orders (intentions that can be cancelled). The footprint shows executed trades (facts that can't be un-traded). They're complementary.
Educational content only. Nothing here is financial or trading advice. Order-flow and options patterns shift probabilities; they never guarantee outcomes.