MT5 Expert Advisors: The Complete Guide to Choosing, Testing, Installing and Running an EA

What an MT5 Expert Advisor is and is not

An Expert Advisor is a compiled MQL5 program, a file ending in .ex5, that runs inside the MetaTrader 5 terminal. It reads prices and indicators, applies its rules, and sends orders to your broker. It can watch the market around the clock while the terminal is running and connected, and it follows its rules every time. It cannot see the future, it does not know about news unless it was coded to, and a strategy that worked in the past can stop working. MetaQuotes explains the platform side in its documentation on trading robots.

Start with the plain-language basics in what is a forex Expert Advisor, then see MT4 versus MT5 to confirm you are on the right platform, and what MQL5 is if you want to know how they are built. The glossary defines every term used here.

Choose a strategy type first

If you are new, a style with a stop loss on every trade is easier to understand and to size. The automated versus manual trading guide and the comparison of EAs, copy trading and signals help you decide whether an EA is the right method at all.

Decide your risk before you pick an EA

The most useful number in automated trading is the amount you accept losing on one trade. Many traders pick about 1 percent of the account or less. From that figure and the EA's stop distance you get a lot size. If the broker's smallest lot already risks more than your limit, the account is too small for that EA. Worked examples in euros are in how much money you need to run an EA.

• Lot size and risk management for EAs explains the method.
• The lot size calculator, gold lot size calculator, pip value calculator and margin calculator do the sums.
• Drawdown explained and the drawdown calculator show why a 50 percent loss needs a 100 percent gain to recover.
• The risk and reward calculator checks whether a target is realistic against its stop.

Install, configure and keep it running

1. 1

   Step 1: Install the EA

   Copy the .ex5 file to the Experts folder, refresh the Navigator and attach it to the right chart. The steps are in the install guide and the longer safe setup walkthrough.

2. 2

   Step 2: Load the setfile and read the inputs

   A setfile is the author's saved settings. See setfile and input settings explained.

3. 3

   Step 3: Give each EA its own magic number

   This stops two EAs managing each other's trades. See running multiple EAs.

4. 4

   Step 4: Run it on a VPS

   A VPS keeps the terminal online. See VPS for MT5 EAs.

5. 5

   Step 5: Fix problems quickly

   If the EA is not trading, start with the AutoTrading and error guide and common MT5 errors.

Test in the right order

Testing is where most protection comes from, and where shortcuts do the most harm. Begin with a backtest in the MT5 Strategy Tester using the mode based on real ticks and your broker's actual costs, which is covered in how to backtest an EA in MT5. Read the report properly with how to read an MT5 backtest report or the shorter Strategy Tester report guide. Know where the data comes from in historical tick data for MT5.

Then guard against false confidence. Optimisation and overfitting explains why a tuned result often fails live, and can EA backtests be manipulated lists the common tricks. Finish with a forward test on demo through a news week, then a live account at the smallest lot.

Pick an instrument you can size

Other topics that shape results: the best timeframe for EAs and how to choose a broker for an EA. Strategy-specific research is in the VWAP gold breakout research and the scalping broker rules research.

Rules that change the setup: Europe and prop firms

If you trade from the European Union, ESMA's retail CFD rules cap leverage at 30 to 1 on major pairs and 20 to 1 on gold, require a 50 percent margin close-out and give negative balance protection. That changes margin and grid behaviour, and it is covered in EA trading in Europe.

If you plan to use a prop firm challenge, loss limits and rules on third-party EAs matter more than the strategy. Start with using EAs with prop firms, which firms allow EAs, EAs not suitable for prop firms, setting up for a challenge, the FTMO example and the prop firm challenge calculator.

Buy carefully

Most losses on the buying side come from skipped questions. Use the EA buying checklist, learn to verify a track record and spot scams, understand lifetime, subscription and rental licences, and read how to buy a cheap MQL5 EA safely and whether free MT5 EAs are safe. When you are ready to compare products, browse the Expert Advisor catalogue or the gold EAs, and read the refund policy first.

1%

A common per-trade risk limit; many traders go lower

3

Test stages: real-ticks backtest, demo forward test, minimum live lot

15

Questions in the buying checklist

Ten beginner mistakes worth avoiding

1. Buying on a screenshot instead of a verifiable record.
2. Attaching a new EA straight to a live account.
3. Using the default lot size without checking the risk in money.
4. Running the EA on the wrong timeframe or symbol name.
5. Putting two EAs on one account with the same magic number.
6. Leaving Allow DLL imports on for files from unknown sources.
7. Optimising settings until the backtest looks perfect.
8. Switching EAs after every small loss, so no system gets a fair sample.
9. Trading through high-impact news with a strategy that is not built for it.
10. Forgetting that the terminal must stay online for the EA to manage trades.

Each one has a fix in the guides above. Work through the checklist in order and most of this list never happens to you.

If you only read five guides

The list above is long on purpose, so you can come back to the part you need. If you want the shortest path, read these five in order. First, the safe setup walkthrough, so you know what installing involves. Second, the guide on backtesting, so you can see how a strategy behaved on past data. Third, the report guide, so you can read what the backtest tells you. Fourth, the buying checklist, so you ask the right questions before you pay. Fifth, the sizing guide, so the first live lot is one you can afford to lose. Everything else deepens one of those five steps.