Order book

First ten Bid and Ask price levels over time

The 20 curves track the first ten Bid and Ask price levels. An update may affect just one level: other levels retain their last price and their curves remain flat. In this educational simulation, levels 1–2 change most frequently, with fewer changes towards level 10. This scenario illustrates activity concentrated near the best prices, rather than a universal rule. Size-only updates do not move these price curves. Each curve follows a book rank, not an individual order; in a real book, an insertion or deletion can also shift several ranks.

Order Book · 10 Bid + 10 Ask00:00 / 01:00

Simulated data · 60-second animation · price by level, without size information.

PauseReplay

Order book can provide enormous insight into a stock's price action. Order book will show you a ranked list of the best bid and ask prices from each of these participants, giving you detailed insight into the price action. Knowing exactly who has an interest in a symbol can be extremely useful, especially if you are day trading.

Additional market data is known as level 2 market data, the order book, or the depth of market, and includes the following additional information:

Highest bid prices: The highest 5 or 10 prices (depending upon the market) that traders are willing to pay to buy a contract Bid sizes: The number of contracts that are available at each of the highest bid prices Lowest ask prices: The lowest 5 or 10 prices (depending upon the market) that traders are willing to accept to sell a contract Ask sizes: The number of contracts that are available at each of the lowest ask prices

Level 2 market data provides the additional information that is needed to trade using trading systems that follow the order flow, and advanced volume based trading systems. Level 2 market data is also known as the order book, because it shows the orders that are currently pending for the market, and is also known as the depth of market, because it shows the number of contracts that are available at each of the available prices.

Order Book example: ten Bid and Ask levels

Three fictional snapshots with microsecond timestamps. Each level contains a Bid price, its displayed size, an Ask price and its displayed size. Scroll horizontally to view all 42 columns on smaller screens.

Date	Time	Level 1				Level 2				Level 3				Level 4				Level 5				Level 6				Level 7				Level 8				Level 9				Level 10
		Bid1	Bid size1	Ask1	Ask size1	Bid2	Bid size2	Ask2	Ask size2	Bid3	Bid size3	Ask3	Ask size3	Bid4	Bid size4	Ask4	Ask size4	Bid5	Bid size5	Ask5	Ask size5	Bid6	Bid size6	Ask6	Ask size6	Bid7	Bid size7	Ask7	Ask size7	Bid8	Bid size8	Ask8	Ask size8	Bid9	Bid size9	Ask9	Ask size9	Bid10	Bid size10	Ask10	Ask size10
10/28/2026	07:01:10.104237	4940.00	88	4940.25	88	4939.75	105	4940.50	111	4939.50	122	4940.75	134	4939.25	139	4941.00	157	4939.00	156	4941.25	80	4938.75	78	4941.50	103	4938.50	95	4941.75	126	4938.25	112	4942.00	149	4938.00	129	4942.25	72	4937.75	146	4942.50	95
10/28/2026	07:01:10.409518	4940.25	101	4940.50	99	4940.00	118	4940.75	122	4939.75	135	4941.00	145	4939.50	152	4941.25	68	4939.25	74	4941.50	91	4939.00	91	4941.75	114	4938.75	108	4942.00	137	4938.50	125	4942.25	160	4938.25	142	4942.50	83	4938.00	159	4942.75	106
10/28/2026	07:01:10.732764	4940.50	114	4940.75	110	4940.25	131	4941.00	133	4940.00	148	4941.25	156	4939.75	165	4941.50	79	4939.50	87	4941.75	102	4939.25	104	4942.00	125	4939.00	121	4942.25	148	4938.75	138	4942.50	71	4938.50	155	4942.75	94	4938.25	77	4943.00	117