Iceberg order

What it is

An iceberg order is a large order that has been broken into small visible slices, where only the current slice sits in the public order book at any given moment. When that slice fills, the next slice is automatically posted at the same price, and the cycle repeats until the parent order is complete. The displayed quantity is the tip of the iceberg; the bulk of the size is hidden.

Icebergs exist because traders with size do not want to advertise it. Posting a single 500-lot bid in a market where the typical resting size is 20 contracts would push price away — counterparties would step in front, momentum traders would chase, and the order would either fill at worse prices or have to be pulled. By showing only 20 at a time, the iceberg participates as a normal-looking limit order while quietly absorbing or distributing the full inventory.

Why it matters

Detecting an iceberg gives a trader a high-quality read on where institutional interest sits. If a level keeps absorbing aggressive volume without the displayed size shrinking in the way it normally would, an iceberg is the most likely explanation. That level becomes a high-conviction reference: support if it sits on the bid side, resistance if on the ask side.

Practical uses include:

• Identifying levels where a long-term participant is accumulating against the prevailing flow.
• Avoiding entries that try to break through an iceberg from the wrong side.
• Anchoring fade trades — when an iceberg is doing the work, the level often holds longer than typical resting size would suggest.

How it appears on Sierra Chart

Sierra Chart does not display icebergs explicitly — by construction they are hidden in the exchange's matching engine and only inferred from behavior. The clues live in the time-and-sales feed and the DOM: a price level that keeps printing aggressive volume but whose displayed quantity oscillates rather than depleting is a classic footprint. Some traders use refresh-count or volume-vs-displayed-size studies built on ACSIL to flag suspect levels automatically.

The Market Depth Historical Graph helps too — comparing how much volume traded at a level versus how much rested at that level over time can highlight the iceberg signature.

Common patterns / pitfalls

• Not every refresh is an iceberg. Multiple independent traders re-posting at a popular level look the same on the tape.
• Spoofing — large displayed orders that get pulled before they fill — is the opposite trap. Conflating the two leads to bad reads.
• Icebergs detected in low-liquidity windows (overnight, holiday sessions) are far less informative than icebergs at RTH structural levels.
• An iceberg eventually exhausts. Trading the level after the iceberg has finished filling is trading old information.

Related SCS studies

Iceberg detection is largely a tape-reading skill. The SCS catalog focuses on order flow visualization — delta candle coloring, single-print and footprint highlighting — that surrounds and contextualizes the levels where icebergs typically operate, rather than offering a dedicated iceberg detector.