Platforms & AutomationEATrading Robot
Expert Advisor (EA)
An automated trading program written in MQL that runs inside MetaTrader and can place, modify and close orders without human input.
What Expert Advisor (EA) means
An expert advisor is a compiled program that attaches to a MetaTrader chart and reacts to incoming price data. On each new tick or bar the terminal calls the program, which can read prices and indicator values, evaluate its rules, and then open, modify or close orders through the broker connection. The scope is broad: an EA can implement a complete strategy, or it can act as a trade manager that only moves stops, scales out of positions or closes everything before a scheduled news release.
Because an EA runs inside the terminal, it stops when the terminal stops. Traders who rely on continuous operation therefore run MetaTrader on a VPS so the program survives a laptop closing, a home internet outage or a reboot. Development follows a standard sequence: code the rules, backtest over historical data, optimise cautiously, then forward test on demo or at minimum position size before committing real capital. Each stage exists to catch a different failure, and skipping the last one is the most common mistake.
The main risk is not a bug but self-deception. Optimisation can always find parameters that would have produced a beautiful equity curve on past data, and those parameters routinely fall apart on data the search never saw. Bought or downloaded EAs deserve particular scepticism, since sellers show optimised backtests, martingale and grid recovery logic can hide a long string of small wins in front of one catastrophic loss, and a vendor's track record is rarely independently audited.
Worked example
An expert advisor set to risk 1 percent per trade on a 10,000 USD account, entering EUR/USD at 1.0850 with a stop at 1.0820, sizes the order at roughly 0.33 lots and submits it within milliseconds of the signal bar closing.
Related terms
- MetaTrader 4 (MT4)The 2005 MetaQuotes retail terminal built around MQL4 expert advisors, hedging accounts and a single-threaded strategy tester.
- MQL (MetaQuotes Language)The proprietary C-like programming language used to build expert advisors, custom indicators and scripts inside MetaTrader.
- BacktestingReplaying a strategy's rules over historical price data to estimate how it would have performed before risking real money.
- VPS (Virtual Private Server)A remote always-on server, often hosted near the broker's data centre, that runs a trading terminal and its automation continuously.
- Curve FittingTuning a strategy so closely to historical data that it captures noise instead of a real edge, and fails on new prices.
Frequently asked questions
What does Expert Advisor (EA) mean in forex trading?
An automated trading program written in MQL that runs inside MetaTrader and can place, modify and close orders without human input.
How does Expert Advisor (EA) work in practice?
Because an EA runs inside the terminal, it stops when the terminal stops. Traders who rely on continuous operation therefore run MetaTrader on a VPS so the program survives a laptop closing, a home internet outage or a reboot. Development follows a standard sequence: code the rules, backtest over historical data, optimise cautiously, then forward test on demo or at minimum position size before committing real capital. Each stage exists to catch a different failure, and skipping the last one is the most common mistake.
What is an example of Expert Advisor (EA)?
An expert advisor set to risk 1 percent per trade on a 10,000 USD account, entering EUR/USD at 1.0850 with a stop at 1.0820, sizes the order at roughly 0.33 lots and submits it within milliseconds of the signal bar closing.
Trade with a regulated broker
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