Hidden and Iceberg Orders

When a large order sits visibly in the order book, other traders can see it and react: they may trade ahead of it, pull their own orders or wait for a better price. Hidden and iceberg orders exist to reduce that information leakage. An iceberg order shows only a small part of its full size; a hidden order shows nothing at all. Both let larger traders buy or sell without advertising their full intentions.

Iceberg orders#

An iceberg order, also called a reserve order, displays a small "tip" in the order book while the rest stays hidden. When the displayed part fills, a new piece of the same size appears at the same price, until the whole order is done.

Hidden orders#

A hidden order is a limit order that does not appear in the visible order book at all. It still trades with incoming orders at its price, but nobody sees it waiting. Some exchanges offer hidden orders; dark pools are entire venues built around non displayed liquidity. See Dark Pools.

The trade off: priority#

Exchanges usually give priority to displayed orders over hidden ones at the same price. That means:

So hiding your size costs you queue position. Large traders accept slower fills in exchange for less information leakage. See Fill Probability and Queue Position.

Spotting icebergs#

Traders who watch the order book and time and sales sometimes detect icebergs:

• A price that keeps trading but never runs out of size. Thousands of shares trade at $42.10 while only 500 ever show on the bid.
• Repeated identical displayed sizes reappearing instantly after fills.
• Volume at a price far above the visible size.

A detected large buyer can act as support, at least until the iceberg is finished. Some order flow traders build strategies around this, though it is far from reliable, since icebergs can be cancelled at any time. See The Order Book and Market Depth.

Who uses these orders#

• Institutions buying or selling large positions over hours or days.
• Algorithmic execution systems, which slice orders into small pieces automatically. See VWAP, TWAP and POV Execution.
• Active traders in thinner markets who do not want their size seen.

For most retail order sizes, there is little benefit: a few hundred shares in a liquid stock do not move the market or reveal much.

Icebergs and hidden orders in crypto and futures#

Several crypto exchanges support iceberg and hidden orders, and futures platforms commonly offer iceberg functionality, sometimes simulated by the trading software rather than the exchange itself. Simulated icebergs are managed by your platform sending new visible orders as each one fills, which means each slice joins the back of the queue.

Frequently asked questions#

What is an iceberg order?#

A large limit order that displays only a small portion in the order book, revealing more as each displayed piece fills.

Are hidden orders legal?#

Yes. Exchanges offer them, and dark pools are regulated venues for non displayed trading.

Do hidden orders get filled more slowly?#

Usually, yes. Displayed orders at the same price typically have priority, so hidden and reserve size fills after visible size.

Sources#

• Wikipedia, Iceberg order