What is an expert advisor?
An expert advisor (EA) is a small program that runs inside MetaTrader 4 or 5 and trades your account according to fixed rules — it watches prices, decides when to buy or sell, and manages the orders without you clicking anything. An indicator, by contrast, only draws information on the chart; it never places a trade.
How an expert advisor actually works
An EA is compiled code (a .ex4 file for MetaTrader 4, .ex5 for MetaTrader 5) written in MQL. Once you attach it to a chart it runs on every price tick and follows three loops: read the market (price, indicators, time, open positions), decide (do the entry rules match?), act (open, modify or close orders through your broker). It keeps doing that for as long as the terminal is open, algo trading is enabled and the chart stays attached — which is why serious users run EAs on a VPS rather than a home PC.
Everything the EA does is a rule someone wrote. It has no judgement, no news awareness beyond what it was programmed to read, and no ability to adapt to a market it has never seen.
EA vs indicator vs script
| Expert advisor | Indicator | Script | |
|---|---|---|---|
| What it does | Trades automatically | Draws / alerts only | One-off task |
| Runs | Continuously | Continuously | Once, then exits |
| Can place orders | Yes | No | Yes |
| Install folder | MQL4/5 → Experts | MQL4/5 → Indicators | MQL4/5 → Scripts |
| Needs Algo Trading on | Yes | No | Yes |
On this site each file is tagged so you know which you are getting; browse MT5 EAs, MT4 EAs or indicators.
Common types of EA
- Trend following — enters in the direction of a moving average or breakout and holds. Fewer trades, larger stops. See trend EAs.
- Scalping — many small trades, very sensitive to spread, slippage and broker execution. See scalping EAs.
- Grid — places a ladder of orders at fixed intervals and profits from oscillation; risk grows if price trends against the grid. See grid EAs.
- Martingale / recovery — increases lot size after a loss to recover it. Equity curves look smooth until one run of losses wipes the account.
- Hedging — holds opposite positions to offset exposure; requires a hedging-type account. See hedging EAs.
- News — trades around scheduled economic releases, where spreads widen dramatically.
Are free EAs profitable?
Honestly: most are not, and no one can tell you a given file is profitable without testing it. A free EA is code of unknown origin with no track record attached — it may be a competent strategy someone shared, a stripped demo, an old version that no longer suits current spreads, or something that only ever worked in a backtest. The realistic way to use them is as material to study and test, not as a shortcut to income.
What separates a usable one from the rest is evidence you gather yourself: a Strategy Tester run over 6–12 months, then several weeks on a demo account with realistic lot sizes, watching drawdown rather than profit. That process is covered in how to test a free EA on a demo account.
What you need to run one
- MetaTrader 4 or 5 on Windows — the mobile apps cannot run custom EAs.
- A broker account (demo is enough to start), with the account type the EA expects — hedging vs netting matters on MT5.
- Algo Trading enabled in the terminal and in the EA's own properties.
- A VPS if you want it running 24/5 without leaving a PC on.
Installation takes about a minute: how to install an .ex4 / .ex5 file.
Is using an EA allowed?
Automated trading is legal and supported by MetaTrader itself; most retail brokers permit it. Individual brokers may restrict specific behaviour — arbitrage, tick scalping or trading within seconds of news — so check your broker's terms if the EA does any of those. Prop-firm accounts usually have their own explicit rules about EAs.
Frequently asked questions
What is an expert advisor in forex?
An expert advisor (EA) is a program that runs inside MetaTrader 4 or 5 and trades an account automatically according to pre-programmed rules — deciding entries, exits and order management without manual clicks.
What is the difference between an EA and an indicator?
An EA places and manages trades; an indicator only displays information or alerts on the chart and can never open an order. They install into different folders (Experts vs Indicators).
Are free expert advisors profitable?
Most are not, and none should be trusted on the basis of the file alone. A free EA has no verified track record — test it in the Strategy Tester over 6–12 months and then on a demo account for several weeks before considering real money.
Do I need to keep my computer on for an EA to trade?
Yes. An EA only runs while the MetaTrader terminal is open with algo trading enabled, which is why most people run them on a Windows VPS so they trade 24/5.
Is automated trading with EAs legal?
Yes — automated trading is a built-in MetaTrader feature and most retail brokers allow it. Some brokers restrict specific tactics such as arbitrage or news scalping, so check your broker's terms.