Expert Advisors (EAs)

What an EA is — and what it isn't

An Expert Advisor is a program that runs inside MetaTrader and places orders according to rules you can read. That's all it is. It executes a strategy exactly as written, without hesitating, revenge-trading, or moving a stop because it "feels" wrong — which is genuinely valuable, since those human failures cost most traders more than bad entries do.

What automation does not do is convert a losing strategy into a winning one. An EA with a negative edge simply loses money faster and more consistently than you would by hand. Every EA here is a mechanical implementation of a specific, openly stated idea — not a black box, and not a machine that prints money while you sleep. If a site offers you one that is, that is the moment to close the tab.

The three strategy shapes

Every EA on this site is one of three shapes, and the shape matters more than the indicator inside it, because it determines what the losing periods feel like. Pick the one you can actually live through.

How to evaluate one before you run it

1. Read the source. Every file here is .mq4/.mq5 text, not a compiled binary, precisely so you can check that the code matches the lesson before you trust it with an order. It usually takes ten minutes.
2. Find the risk logic first. Where does the stop loss go, and is the lot size fixed or calculated from account balance? An EA without a stop loss is not a strategy — it is a bet that no move will ever be large enough to matter.
3. Backtest, then distrust the backtest. Run it in the Strategy Tester over several years and multiple pairs, then read Backtesting Basics to understand why a beautiful result is often an artefact of tick quality, spread assumptions, or parameters fitted to that exact history.
4. Forward-test on demo. Weeks, not days, and through at least one high-impact news event. Live spreads, slippage, and requotes behave nothing like historical data.
5. Size it so a bad month is survivable. The parameter that decides whether you are still trading in a year is lot size, not indicator period — see Risk Management Basics.

The risk engine every EA here shares

Every EA on this site runs the same risk engine on purpose. Entry logic is the experiment — the thing each lesson exists to teach — while stops, targets, position sizing, and the safety checks are held constant, so that comparing two EAs compares their ideas rather than two different risk configurations. Rather than restating that machinery on all 35 pages, it is documented once here; each EA's own page covers only the parameters specific to its strategy.

Stop Loss. Most EAs size the stop from ATR: SL distance = ATR (ATRPeriod, default 14) × ATRMultiplier (default 2.0), so a volatile pair automatically gets a wider stop and a quiet one a tighter stop. A few structure-based EAs — Fractals, Ichimoku, and Parabolic SAR — instead place the stop at the level their own pattern defines, and say so on their page.

Take Profit. TP distance = SL distance × RiskRewardRatio (default 2.0), so every trade carries a known risk-to-reward ratio no matter which pair or timeframe it runs on.

Position sizing. Lot size is calculated exactly as taught in Risk Management Basics: RiskPercent (default 1.0%) of account balance ÷ stop distance, converted through the symbol's tick value and normalized to the broker's minimum, maximum, and lot step (see Lot Sizes Explained). A losing trade therefore costs roughly the same fraction of the account whether the stop is wide or narrow. Traders who prefer a constant size can enable UseFixedLot, which overrides the calculation with FixedLotSize (default 0.01).

Safety checks. Four mechanics gate every order. The EA evaluates its signal once per completed bar — never tick by tick — so one qualifying bar cannot fire repeated entries. It holds one position at a time, counting open trades filtered by symbol and its own magic number before considering a new one. Each EA carries a unique MagicNumber (listed on its page), so it never touches trades opened manually or by another robot on the same account. And if the current spread exceeds MaxSpreadPoints (default 30), the entry is skipped entirely rather than filled at a bad price — the concern covered in Spread and Slippage. EnableTrading is the master on/off switch for pausing an EA without removing it from the chart.

Practical requirements

Automated trading needs MetaTrader running continuously with AutoTrading enabled, a stable connection, and a broker that permits EAs on your account type. Closing the terminal stops the EA — open positions stay open, but no new orders or exits are managed, which is why traders who run EAs seriously use a VPS rather than a laptop. Check your broker's rules on automated trading and on the strategies they allow before you start.

New to this? Work through the basic lessons first, then the indicator lessons for whichever tool sits at the heart of the EA you're considering. Running a robot whose signal you can't explain means you have no basis for deciding whether a losing streak is normal variance or the strategy breaking down — and that decision is the whole job.