# Spot iceberg orders on Level 2 > How Scalpel flags an iceberg: one venue refilling a small size while far more trades there, the exact rule behind the icon, and why it is not a floor. Source: https://scalpeltrade.com/guides/iceberg-orders Guide 3.2, Reading the market. Intermediate, 6 min read. Checked with Scalpel 1.12.8 on 2026-10-15. By Scalpel Team. **In short:** An iceberg is a big order that shows only a small piece of itself on the book and refills as it trades. Scalpel marks one with a layers icon on the venue's row when, within 20 seconds, that venue's quote at one price is hit at least 3 separate times, $15,000 or more trades into it, at least 3 times the most it ever showed, and the price still holds. The read line then says **Hidden seller refilling at the offer** or **Hidden buyer refilling at the bid**. It tells you a large order is working there now; it does not tell you the level will hold. Big traders rarely show their full size. A fund selling 50,000 shares will display 100 or 200 at a time on one venue and let the exchange refill it each time it trades, so the book never shows the wall. Watching the tape against the book is how you catch it: far more stock trades at a price than was ever displayed there. Scalpel does that watching for you, on every desk. **Before you start:** - Know your way around the Level 2 panel ([guide 3.1](https://scalpeltrade.com/guides/read-level-2)). ## What it looks like *Screenshot: IEX keeps showing 145 shares at 5.71 (1) while buyers lift far more there (3). The layers icon marks the row and the read line says **Hidden seller refilling at the offer** (2). Demo data.* - **The icon** sits in the slot beside the price: left of the price on the bid side, right of it on the ask. On the coloured rows (**By price tier** or **By venue**) it is drawn dark, like the row's text. - **With colouring Off**, the icon is cyan and the price turns cyan too, so it stands out on the plain rows: *Screenshot: The same iceberg with Coloring set to Off: the price and the icon in cyan. Demo data.* - **The read line** under the summary bar takes its own cyan layers icon and names the side: **Hidden seller refilling at the offer** for an iceberg on the ask, **Hidden buyer refilling at the bid** for one on the bid. If there is one on each side, it names the seller. - **With grouping on** (the **-** **Tick** **+** stepper), the icon marks the grouped row that contains the iceberg's price. ## The exact rule Scalpel watches each venue's quote at each price separately. A row gets the icon when all of these are true within a rolling 20-second window: | Test | Threshold | |---|---| | Separate hits on that venue's quote | 3 or more. Prints less than 1 second apart count as one hit, so one sweep is not three tests. | | Dollars traded into it | $15,000 or more (shares x price). | | Traded against shown | At least 3 times the most that venue displayed at that price in the window. | | Still showing | The venue is still quoting size at that price after the hits: it refilled. | | Price holding | The inside has not moved past it: for a hidden seller the best ask is still at that price or lower, for a hidden buyer the best bid is still there or higher. | Only lit prints count, the trades that happen on an exchange's displayed book. Off-exchange prints never touched the book, so they cannot refill it. **When it clears.** The icon stays for up to 30 seconds after the rule last fired, as long as the level holds. It goes sooner if a lit trade prints through the price (above a hidden seller, below a hidden buyer) or the inside moves away from it. It can fire again for the same venue and price after 20 seconds. ### A worked example In the shot, IEX displays 145 shares at 5.71 and never more. Over 15 seconds, buyers lift IEX's offer in three separate bursts of 900, 1,200 and 800 shares: - 3 hits, more than a second apart: passes. - 2,900 shares x $5.71 = $16,559 traded: over $15,000, passes. - 2,900 shares against at most 145 shown is 20 times: over 3 times, passes. - IEX is still showing 145 at 5.71, and the best ask is still 5.71: passes. The icon goes on IEX's row. Someone with a lot more than 145 shares is selling at 5.71. Why so strict: a busy price on a momentum stock refills all the time because many different traders join it, spread across venues. One venue's quote pinned at a small size while it trades many times that size is the pattern of one reserve order, and the $15,000 floor keeps small odd-lot activity from setting it off. ## How to trade around it Scalpel is long only, so the two cases mean different things for you: - **A hidden seller at the offer, above you or where you want to buy.** Every share you buy there comes from a seller with more stock than the book admits. A breakout into a hidden seller can stall until the seller is done. Many traders wait for the icon to clear because a lit trade printed **above** the price: that is the seller finished or gone, and the offer is open. Buying into the iceberg itself is buying where supply is deepest. - **A hidden buyer at the bid, under your long.** It is tempting to treat it as a floor and put your stop just under it. Don't rely on it (see below). Put your stop where your trade is wrong, whatever the book shows ([guide 5.1](https://scalpeltrade.com/guides/how-stops-work)). Icebergs are one of several behaviours that give away a big trader; the others (unusual size, size pulled as price comes near, bids stepping up, who is hitting and lifting) are in [guide 3.7](https://scalpeltrade.com/guides/read-the-players). **This can cost you money: A hidden buyer is not a floor.** When the iceberg reads were replayed over recorded sessions, levels with a hidden buyer broke within a minute **more** often than ordinary levels, not less: the hidden order gets filled, and once it is done there is nothing left at that price. An iceberg tells you who is there now, not what happens next. ## What it cannot see - **Off-exchange buying and selling.** Dark pools and internalised retail orders never show on any book. - **Icebergs that move.** A reserve order that re-prices with the market, or splits across venues, does not keep one venue's quote pinned and will not trip the rule. - **Small ones.** Under $15,000 traded in 20 seconds, nothing is flagged, by design. - **Spoofing.** Size shown and pulled to mislead is the opposite pattern: watch for size that vanishes as price approaches ([guide 3.1](https://scalpeltrade.com/guides/read-level-2#reading-players-from-behaviour)). The full story of the replay is in the blog post [Reading the Level 2 montage](https://scalpeltrade.com/blog/reading-the-level-2-montage). ## Questions **What is an iceberg order?** A large limit order that displays only a small part of its size on the book and automatically refills as that part trades, so the full size stays hidden. **How does Scalpel detect iceberg orders?** Within 20 seconds, one venue's quote at one price must be hit at least 3 separate times, with $15,000 or more and at least 3 times its largest displayed size trading into it, while it keeps showing size there and the price holds. Only lit exchange prints count. **Why is the iceberg icon dark on some rows and cyan on others?** On the coloured rows (by price tier or by venue) it is drawn dark like the row's text. With colouring off it is cyan, and the price turns cyan too. **Does a hidden buyer mean the price will hold?** No. In replay, levels with a hidden buyer broke within a minute more often than ordinary levels, because the hidden order gets filled. Place your stop where your trade is wrong, not just under an iceberg. **How long does the iceberg icon stay?** Up to 30 seconds after the rule last fired, while the level holds. A lit trade through the price, or the inside moving away, clears it sooner.