A-Book vs B-Book brokers in plain language
A simple yet precise explanation of A-Book and B-Book: the order execution path, internalization, the Hybrid model, the role of the risk team, and why the user usually does not choose this model themselves.
- Educational article
- ~12 min read
- BrokerLauncher content team
- A-Book · routes exposure to LP
- B-Book · keeps exposure in-house
- Hybrid · mix based on risk policy
- Risk Engine · routing decision
The user usually does not choose this model themselves; the decision is made by the broker risk team.
A-Book and B-Book are two different ways of managing exposure at a forex broker. Rather than being account types that a user picks, these terms describe the broker's internal risk management policy.
In this article we explain A-Book and B-Book in simple but technical terms: the order execution path, internalization, the Hybrid model, the relationship between client PnL and the broker, and the role of the risk team.
This article is intended only as educational material about forex broker execution models and should not be taken as trading advice, legal advice, or a definitive judgement on any broker's performance.
What is A-Book?
In A-Book, the broker routes the exposure created by a client order to one or more external counterparties — for example, a liquidity provider, a prime broker, or an ECN/STP network. In this model, the broker is mostly an intermediary and earns its revenue from spread markup and commission.
Key points about A-Book
- · Exposure is routed to an LP, prime broker, or ECN.
- · The broker's revenue model is typically spread + markup + commission.
- · Latency, slippage, rejections, and partial fills can still occur.
- · The broker is not the primary counterparty to the client's outcome.
A-Book does not mean "execution without slippage" or "full transparency". Execution quality depends on the LP, routing, bridge, and broker policy.
What is B-Book?
In B-Book, instead of routing exposure to the external market, the broker keeps it in its internal structure — a practice known as internalization. From a risk management perspective in this model, client profits can translate into broker losses and client losses into broker profits. For this reason, risk management plays a very serious role here.
Key points about B-Book
- · Exposure is kept internally.
- · From an internal perspective, client PnL is inverted relative to broker PnL.
- · Requires a serious risk engine, aggregate hedging, and compliance.
- · Many brokers keep only part of the flow in B-Book, not all of it.
Does the user choose A-Book or B-Book?
In most forex broker setups, the user does not directly make this decision. The order execution path and exposure handling are determined by the risk management team, dealing desk, or risk engine of the broker, in line with company policy.
Accounts labelled "ECN", "Raw", or "Pro" do not necessarily mean full A-Book. These names usually describe the type of pricing and commission, not the broker's internal routing policy.
Client profile
Trade history, strategy, volume, and client behaviour all feed into the routing decision.
Flow type
Toxic flow, high-frequency, and arbitrage strategies are typically routed differently from a regular trader.
Risk policy
Exposure limits at the symbol, asset-class, or whole-book level shape the final decision.
A-Book vs B-Book differences
| Criterion | A-Book | B-Book |
|---|---|---|
| Order routing | Routed to LP / prime broker / ECN. | Held internally (internalization). |
| Broker revenue model | Spread + markup + commission. | Spread + commission + internal P/L depending on risk management. |
| Exposure | Passed on to the LP. | Partially kept on the internal book. |
| Liquidity dependence | Depends on LP quality and depth. | Depends on the risk engine and broker hedge policy. |
| Risk management | Relatively simpler, since market risk is passed to the LP. | Very serious; requires a strong risk engine and aggregate hedging. |
| Conflict considerations | More limited, since the broker is not the primary counterparty. | Potentially higher; that is why transparency and compliance are critical. |
| User experience | Latency and slippage can occur depending on LP and bridge. | Depending on the risk engine, spreads can be steadier or requotes more frequent. |
Order routing
A-Book: Routed to LP / prime broker / ECN.
B-Book: Held internally (internalization).
Broker revenue model
A-Book: Spread + markup + commission.
B-Book: Spread + commission + internal P/L depending on risk management.
Exposure
A-Book: Passed on to the LP.
B-Book: Partially kept on the internal book.
Liquidity dependence
A-Book: Depends on LP quality and depth.
B-Book: Depends on the risk engine and broker hedge policy.
Risk management
A-Book: Relatively simpler, since market risk is passed to the LP.
B-Book: Very serious; requires a strong risk engine and aggregate hedging.
Conflict considerations
A-Book: More limited, since the broker is not the primary counterparty.
B-Book: Potentially higher; that is why transparency and compliance are critical.
User experience
A-Book: Latency and slippage can occur depending on LP and bridge.
B-Book: Depending on the risk engine, spreads can be steadier or requotes more frequent.
What is the Hybrid model?
In practice, many forex brokers do not run a pure A-Book or pure B-Book model. Instead, they run a Hybrid model in which part of the flow is routed to an LP and part is held internally. The risk engine makes this decision based on several factors:
- Client profile and trading history.
- Strategy type (e.g. scalping or swing).
- Order size and its effect on aggregate exposure.
- Detection of toxic flow and latency arbitrage.
- Long-term profitability profile of the client.
- Market volatility and liquidity conditions.
- Exposure limits at the symbol, asset-class, and whole-book level.
- Overall company risk management policy.
How is PnL managed in B-Book?
When exposure is kept internally, client PnL directly affects the broker's internal PnL. The broker has several tools to manage this risk:
Exposure monitoring
The risk engine monitors exposure in real time at the symbol, asset-class, and whole-book level.
Risk limits
Explicit caps on maximum exposure per symbol or asset class are configured.
Aggregate hedging
The broker can hedge all or part of the exposure with an LP or prime broker.
Dynamic routing
The risk engine can switch a client or a flow type from B-Book to A-Book.
Pros and cons of each model
A-Book
Pros: fewer conflict considerations, a more transparent execution structure, suitable for high volume and precise strategies.
Limitations: dependence on LP quality, possible wider spreads in thin liquidity, and latency and slippage are still possible.
B-Book
Pros: steadier spreads in normal conditions, more flexibility for small-volume retail users, continuous liquidity.
Limitations: potentially higher conflict considerations, a serious need for a risk engine and compliance, and quality can vary widely between brokers.
Is B-Book always bad?
No. B-Book by itself is not a sign of fraud or wrongdoing. It is a common risk management model in retail forex, evaluated alongside regulation, compliance, transparency, and risk engine quality. The real problem is not "being B-Book" but rather a lack of transparency, lack of regulation, poor execution quality, or absent risk controls.
Similarly, A-Book is not absolutely "always better". A-Book execution quality depends on the LP, bridge, routing, and broker policy. In an A-Book broker with a weak LP, slippage and rejections can be worse than at a B-Book broker with a strong risk engine.
Role of the risk team and dealing desk
The A-Book/B-Book/Hybrid decision is ultimately an infrastructure and operations decision. The risk infrastructure plays a key role in the health of a broker:
Risk engine
Decision engine for order routing based on pre-defined rules and real-time client behaviour.
Exposure monitoring
Real-time view of exposure across symbols, asset classes, and the whole book.
LP hedge routing
Sends excess exposure to one or more LPs according to hedge rules.
Dealing desk
Human oversight of unusual market conditions, abnormal behaviour, and urgent decisions.
A-Book/B-Book is more than a label
A-Book and B-Book are two internal policies for managing exposure, and in practice many brokers run Hybrid setups. These labels alone are neither a guarantee of "being good" nor a definitive sign of "being bad". What really matters is the broker's infrastructure, trade execution policy, risk engine, regulation, transparency, and support quality.
FAQs
What is a market maker broker?
The dealing desk model and its relationship to B-Book.
Liquidity provider
The role of LPs in A-Book and aggregate hedging.
What is slippage in trading?
Slippage as an execution-quality indicator.
How spread is calculated
Spread cost and its relationship with the execution model.
MetaManager
The MT5 tool for account management and routing.
Instrument grouping
Symbol groups and different execution policies.
Designing broker routing & risk engine
If you are designing a broker's A-Book/B-Book and risk engine policy, review the liquidity, MetaManager, dealer training, and regulation services at BrokerLauncher.