Install an EA on MT4 or MT5

Before you start

Open a demo account with the broker whose platform you will use. A demo uses fake money and real-looking prices, so it is the right place to find out whether an EA loads, trades and sizes as you expect. Know too which platform you have, because MT4 files do not run on MT5 and the other way round. The MT4 versus MT5 page lists the differences.

Only use an EA file you trust. A file can do anything the platform lets it, including placing orders. If you did not write it, read what it says it does and where it came from, and run it on a demo first.

Install it, step by step

1. Close or leave the platform open. Either works, but you will need to refresh the list if it is open.
2. Open the data folder. In the platform, look under the File menu for an option to open the data folder. The name varies by version.
3. Find the Experts folder. Inside the data folder there is a folder for MQL4 (MT4) or MQL5 (MT5), and inside it a folder called Experts.
4. Copy the EA file in. Put the .ex4 or .ex5 file there. If you have source code (.mq4 or .mq5) it may need compiling in the editor first, which is built into the platform.
5. Refresh the list. In the Navigator panel, right click Expert Advisors and choose Refresh, or restart the platform. The EA should now be listed.
6. Allow automated trading. There is a button on the toolbar, usually labelled Algo Trading in MT5 and AutoTrading in MT4. It must be on, which is often shown in green.
7. Open a chart. Pick the pair and the time frame the EA was made for.
8. Attach the EA. Drag it from the Navigator onto the chart, or double click it. A settings window opens.
9. Check the Common tab. Make sure live trading or algorithmic trading is allowed for this EA. Do not tick extras you do not understand, such as allowing imports of outside code, unless the EA needs them.
10. Set the inputs. This is where the lot size, the stop distance and the limits live. Read each one. The defaults are the author's choice, not yours.
11. Press OK. The EA starts.

How to tell it is running

• In the top right of the chart there should be the EA name with a smiling face in MT4, or a small icon in MT5, not a frowning face or a crossed one.
• The AutoTrading or Algo Trading button is on.
• The Experts tab in the Terminal panel at the bottom shows a line saying the EA was loaded. Open the Journal tab as well.
• Many EAs draw text or lines on the chart, or print a line on every bar. Check what yours should show.

A running EA that has not traded is not necessarily broken. It trades when its rules say so, which may be rarely. Give it time and read the log.

Why it does nothing: the usual causes

• Automated trading is off. The toolbar button, or the setting inside the EA window, is off. This is the most common cause.
• The market is closed. No new prices arrive at weekends or outside a pair's hours.
• Wrong pair or time frame. The EA was made for a different one and its rules never fire.
• A filter is blocking it. A spread limit, a time window or a news filter can keep it from trading all day.
• The account does not allow it. Some account types, or an investor (read only) password login, do not allow trading by a program.
• Not enough margin, or the lot is wrong. The order is refused. See the worked example below.
• The platform lost its connection. The bottom right corner of the platform shows the connection state.
• The file is for the other platform. An .ex4 file will not run on MT5.

The log is your friend. A refused order usually leaves a line with a reason such as invalid volume, not enough money or trading disabled. Read it before changing anything.

Worked example: a lot that is too small to place

This example is made up. An EA sizes each trade to risk 1 percent of the balance with a 20 pip stop. On the pair, one pip on a standard lot is about $10. The platform allows lots in steps of 0.01 with a minimum of 0.01.

On the $100 demo the EA asks for 0.005 lot. That is under the 0.01 minimum, so the order is refused and the EA looks dead. In the log it would show a volume error. On $500 it asks for 0.025, rounds down to 0.02 and risks 0.80 percent. The rounding also means the risk you set and the risk you get differ. The lot size calculator shows the unrounded figure for your own stop.

After it runs: what to check on the demo

• Does it open trades at the times and prices its rules say? Check the first few by hand.
• Are the lot size and stop what you set? Look at an open order.
• Does it close trades as expected, and do stops sit on the broker's server?
• What are the real spread and slippage compared with those in your test?
• What does it do if you restart the platform with a trade open? Some EAs lose track of their own trades.

Run it for several weeks before judging it, since a few trades say little. If it is to run all day, a stable machine matters too, as the forex VPS page explains. For how to test the idea itself, see backtesting.

What this page does not tell you

It does not cover every version or every broker build, and menu names differ. It does not say any EA is safe or profitable. The numbers are made up. Use your platform's own help for the exact steps.