Order book

An order book is an exchange's live list of the buy and sell orders waiting for one trading pair, such as USDC/EUR, sorted by price. Buy orders, called bids, sit on one side and sell orders, called asks, on the other, and a new order fills against the best price on the opposite side.

A euro order book at 10:13 UTC

What would you be selling into if you swapped USDC for euros on exchange Kraken? Its public order book feed answered at 10:13:50 UTC on November 10, 2026 with 309 price levels of buy orders and 310 of sell orders. These were the three closest to the middle.

Bid, euros per USDC USDC wanted Ask, euros per USDC USDC offered
0.8911 632,101.779 0.8912 4,746.903
0.8910 583,388.348 0.8913 330,297.759
0.8909 519,815.465 0.8914 686,228.075

Each row lumps together every order resting at one price. Kraken’s pre-trade feed, read three seconds later, counts them, and it showed 17 separate orders behind the best bid and only one behind the best ask.

How the queue works

Kraken’s trading rules describe a central limit order book matched by price, then by time. The best price fills first, and among orders at one price the oldest goes first. Change the price on a resting order and it drops to the back of the queue at its new price.

Some waiting orders are invisible. A Kraken help article says stop-loss, take-profit and trailing-stop orders stay out of the visible book until they trigger, and the rules describe iceberg orders, which show only a slice of their size at a time.

What an EU platform must publish

MiCA turns the book into public data. Article 76(9) requires the operator of a crypto trading platform to make its bid and ask prices public, along with the depth of trading interest at each, without a break during trading hours.

Article 76(10) adds the price, volume and time of each trade, “as close to real-time as is technically possible.” Under Article 76(11) the data must become free 15 minutes after publication and stay up for at least two years. Article 76(15) has the platform keep order data for at least five years or give its regulator access to the book.

Kraken’s pre-trade endpoint sits under a heading called Transparency in its developer documentation, which says it returns the top 10 levels for each pair.

Read the top, not the tail

A full book can look far deeper than it is. Exchange Coinbase’s level 2 book for BTC-USD, read at 10:13:49 UTC, held 16,595 bid prices and 22,397 ask prices. The lowest bid was $0.01 and the highest ask $138,991,023.41, with the market near $74,295.

Orders that far out play no part in an ordinary sale. What counts for a sale is how much sits within a fraction of a percent of the best price, the question that liquidity measures.

Kraken’s order types page warns that the book “can change significantly since the last traded price, especially in less popular trading pairs.” Before a large sale, open the depth view and add up the bids near the top yourself.

Where it comes up