STP and ECN are widely used descriptions in online trading, but they do not tell the whole story of an execution arrangement. Straight-through processing, or STP, generally describes automated handling. An electronic communication network, or ECN, describes an electronic environment that brings together executable interest from participants or connected liquidity sources.
A broker may use elements of both. The useful questions are not limited to the label: who is the counterparty, how is the price formed, where can the order go, what rules apply and how are execution results reviewed?
What STP usually means
Straight-through processing means that eligible instructions move through connected systems with limited manual intervention. In a trading route, an order can pass from the client platform to a trade server, through risk and account checks, and onward to an internal or external execution destination.
Automation can also create a clearer audit trail because system events can be timestamped and linked across order, deal and position records. That evidence is useful only when clocks, identifiers and retention practices are consistent across the connected systems.
Automation can improve consistency and reduce handling time. It does not remove controls. An order may still be checked, rejected, partly filled, routed differently or held under rules defined by the account, instrument and execution policy.
Automation is not a counterparty definition
STP describes processing, not necessarily the legal relationship. A provider may act as principal, agent or use a mixed model under its terms. It may hedge some exposure externally while internalising other flow. The account agreement and execution policy are more authoritative than a short marketing label.
What an ECN is
An ECN is an electronic system that can match or route trading interest among participants. In retail foreign exchange, the term is also used more broadly for account routes connected to aggregated external liquidity and variable raw pricing.
The exact arrangement varies. Some environments display depth from connected sources; others supply only the best available bid and ask. Commission, minimum size, fill policy and eligible instruments can differ by account.
ECN does not mean one global book
The foreign exchange market is decentralised and fragmented. Trading takes place through dealer relationships, multibank platforms, single-dealer platforms, exchanges and other venues. BIS research shows that a substantial share of customer trading is internalised within dealer liquidity pools. One platform therefore represents its connected execution environment, not all global liquidity.
How liquidity aggregation works
A liquidity aggregator receives executable quotes from multiple sources and organises them into a combined view. At a simple level, it can compare bids and asks, quantities and source conditions. The resulting top price may be available for only a limited amount.
Price and quantity travel together
A quote is not just a number. It is normally associated with a quantity, time and set of conditions. If a market order is larger than the amount available at the best level, the remaining quantity may trade at other levels, be partly filled or be rejected under the applicable fill policy.
That is why a 0.0 pip quote should not be treated as the guaranteed cost or price for every order.
What routing logic may consider
No routing system can compare liquidity that it cannot access. The quality of the available route therefore depends on the connected sources, their current quotes and the rules governing access. Adding more sources can broaden the comparison, but it can also add differences in response time, minimum size and rejection behaviour.
Routing systems may consider displayed price, available size, venue eligibility, response time, historical fill quality, transaction cost and other controls. Best execution obligations can require firms to consider factors beyond speed or headline price, depending on the jurisdiction and client classification.
Some orders can be split across sources. Others may be sent to one destination. A broker's execution policy should explain the material factors and venues it uses, while transaction records show what happened to an individual instruction.
Co-location and bridges
A bridge connects a trading platform with another pricing or execution system. Co-location places systems in the same or nearby data centre to reduce network distance. Both can support a faster electronic route, but neither creates liquidity or guarantees acceptance.
Our guide to trading latency and order execution explains how network and processing time fit into the wider chain.
Why orders can have different outcomes
Two orders submitted close together can receive different results if price, available quantity or venue responses change between them. Order size, direction and fill instructions also matter. News and session transitions can cause liquidity providers to update or withdraw quotes quickly.
Slippage may be favourable, adverse or zero. A market order accepts available prices, while a limit order prevents execution beyond its limit but may remain unfilled. The explanation of active markets and difficult fills covers this interaction in more detail.
Questions to ask about an execution model
- Which entity is the contractual counterparty?
- How are prices formed and which mark-ups or commissions apply?
- Can orders be internalised, externally hedged or routed to more than one source?
- Which order types, fill policies and rejection rules apply?
- How are conflicts managed and execution quality monitored?
- What transaction evidence is available if a fill is queried?
The ECN account page describes the available account features, but the current legal terms, product schedule and execution policy remain the controlling documents.
Read the label in context
STP and ECN can identify useful parts of a modern electronic trading route. They are not certifications and they do not settle every question about pricing or execution. Read them alongside the provider's counterparty model, order rules, venue information, costs and actual execution evidence.