What is an expert advisor (EA) in MetaTrader 5?

An expert advisor (EA) is a program that sits on a MetaTrader 5 chart and opens, adjusts and closes trades by itself, following fixed rules. So what is an expert advisor compared with a trading bot? The same thing. EA is just the name MetaQuotes, the company behind MetaTrader, uses for a trading bot on its own platform. On cTrader the same thing is called a cBot.

The name only describes the technology. Whether an EA makes you anything depends on things the word does not tell you: who runs it, where it runs and how its risk is set. That is what this piece is about, along with five checks a beginner can use to judge an EA without reading a single line of code.

What is an expert advisor in MetaTrader 5?

A piece of code written in MQL5, MetaTrader's programming language, that reacts to the market. The MQL5 documentation calls it an automated trading system linked to a chart.

Every time a new price comes in, a tick, the EA gets a nudge. It holds that price up against its rules and decides. Do nothing. Open an order. Move a stop, or close a position. Those orders go straight to your broker's server without you clicking anything.

Two practical rules from the MetaTrader 5 manual. Only one EA can run per chart, so if you want two working, you open two charts. And an EA keeps going until you remove it from the chart or close MetaTrader.

Think of an EA as the engine. How hard that engine pushes, and in which direction, sits in its settings. Two people running the exact same EA can get completely different results: one at half a percent risk per trade, the other on the default lot size with an account far too small for it.

What is the difference between an EA, an indicator and a script?

The Navigator in MT5 has more folders than just Expert Advisors. Beginners mix them up all the time, and some sellers are happy to let them. According to MetaQuotes it works like this:

• Expert advisor: sits on a chart, reacts to every tick and is allowed to trade. Lives in the MQL5\Experts folder.
• Indicator: calculates and draws, like a moving average or the RSI. An indicator cannot trade by itself, it only does analysis. You can put as many on one chart as you like.
• Script: carries out one action once, for example closing every open order, and then drops off the chart. It does not come back after MT5 restarts.

There are also services, which run in the background without a chart. As a beginner you will rarely meet one.

Watch out for so-called signal indicators that paint arrows on your chart. They never open a trade. You still have to click. Anyone selling one of those as a bot is selling you something other than you think.

Then the files. An EA comes in two forms. The .mq5 file is the source code, the text a programmer writes. MetaEditor compiles it into an .ex5 file, and that is what MT5 actually runs. The MetaEditor manual says an .ex5 can be distributed without the source. That is why almost every paid EA arrives as an .ex5: you can use it, but you cannot read what is inside. If you are curious what writing your own EA involves, read our piece on MQL5 or Python for a trading bot.

How can you tell an EA is actually allowed to trade?

Dragging an EA onto a chart is not enough. There are two locks, and both need to be open.

The first lock is the Algo Trading button in the toolbar at the top. It switches automated trading on or off for the whole of MetaTrader. In MT4 and in older guides it is called AutoTrading, and even the official MetaTrader 5 help page still uses the old name. The platform itself has said Algo Trading since at least late 2021. In November 2021 someone on the MQL5 forum asked where his AutoTrading button had gone. The moderator's answer: same button, different name.

The second lock is per EA. When you start one, a window opens with a Common tab, and that tab has the box that allows algo trading. Without that tick the EA runs, but it is not allowed to do anything.

You can see whether everything is set up in the top right corner of the chart. The EA's name appears there with a small mortarboard hat icon. Blue means it is running and allowed to trade. White or grey means it is loaded but blocked. No icon means it never loaded.

The smiley face from countless YouTube videos belongs to MT4. In November 2023 an experienced member of the MQL5 forum still had to explain that you will never see that face in MT5. If in doubt, check the Experts tab at the bottom of the window. The EA reports there what it is doing, and why it is not doing something.

Why does an EA stop when you close your laptop?

Because an EA runs inside your MetaTrader, on your computer. It does not live at your broker.

Shut the lid, lose your wifi or let Windows install an update overnight, and the EA stands still. Your open positions stay with the broker, but nobody is watching them. A stop loss already placed with the broker keeps working. A trailing stop the EA manages itself does not.

MetaQuotes says as much in the guide to its own hosting service: a robot, a purchased EA or a signal subscription needs a constant connection to the trade server and a power supply that never drops. That is why serious EAs run on a VPS, a computer in a data centre that is always on. MetaQuotes rents these out itself through MQL5 and lets you pick a server close to your broker, so your orders arrive faster. Independent VPS providers work too.

That gives you the first question to ask about any EA or bot you are considering. Where does it run, and who notices when it stops?

What are you actually buying on the MQL5 Market?

The MQL5 Market is the shop built into MetaTrader itself, and it is big. Back in September 2018 MetaQuotes counted 13,970 products, including 4,800 robots and 6,500 indicators. The list of MT5 robots alone ran to 246 pages when this piece was written.

Read the Market rules before you pay. A paid product costs at least 30 dollars. You get at least 5 activations, so you can install it on a few computers or VPSs, and the seller may allow up to 20. MetaQuotes keeps 20 percent of every payment. Most important of all: what you buy on the Market cannot be returned. Not even if the EA drains your account in the first week.

Renting is an option too, for a month for example. For a beginner that is nearly always the smarter first step.

An EA on the Market comes with a demo version. It runs only in the Strategy Tester, MT5's backtester, never on a live chart. Useful for seeing how it trades. But a backtest shows what would have happened. It cannot tell you what happens tomorrow.

How do you judge an EA with five checks?

You do not need to read MQL5 to judge an EA. You need to ask the right questions. You can run these five against any EA, any bot and any seller.

1. Is there a live track record of at least a few months? On a real account, visible through a third party, such as a signal on MQL5 or a connected Myfxbook page. A screenshot of a backtest is not a track record. Neither is a demo account, where your orders always fill neatly.
2. What does it do with a losing trade? A healthy EA takes the loss at a fixed stop. If the history shows the lot size going up after a loss, or ten positions open in the same direction, you are looking at martingale or grid. Those curves look beautiful for months, right up to the day there is no money left to add. Read how that ends in why martingale and grid bots blow up accounts.
3. How much does it risk per trade, and can you see it? Ask in percent of your account, not in lots. A fixed 0.10 lot with a 50 pip stop on EURUSD costs about 50 dollars per losing trade. On a 10,000 dollar account that is half a percent. On 1,000 dollars it is five percent.
4. Where does it run, and who keeps an eye on it? On a VPS or on your laptop? And who notices if it stops at three in the morning, or if your broker changes its server time? With an EA from the Market, that person is you.
5. Is the backtest honest? Check whether the test covers violent periods like March 2020, and whether it was run on real ticks with a realistic spread. On gold the standard spread usually sits around 2 to 3.5 pips, which is 0.20 to 0.35 dollars. A gold backtest with a spread of almost zero is fiction. There is more on this in our piece on why backtests mislead.

If an EA already fails check 1 or 2, you can skip the rest.

What else do beginners ask about expert advisors?

Is an expert advisor the same as a trading bot?

Yes. EA is the name MetaTrader uses for a trading bot. It is a program written in MQL5 that sits on a chart and opens and closes orders by itself. The name says nothing about whether the bot is any good. That depends on the strategy, the risk settings and where it runs.

Does an EA work when my computer is off?

No. An EA runs inside MetaTrader on the computer where the platform is open. If that machine is off or loses its connection, the EA does nothing. Open positions stay with the broker. That is why most people run an EA on a VPS that is on day and night.

Can I get a refund if an EA I bought disappoints?

Not on the MQL5 Market. Its rules say purchased products cannot be returned. Test the demo version in the Strategy Tester first, or rent the EA for a month before you buy it.

Why is the hat icon next to my EA white or grey?

White or grey means the EA is loaded but not allowed to trade. Switch on the Algo Trading button in the toolbar and tick the option that allows algo trading in the EA's settings. Blue means it is running and allowed to trade.

What is the difference between an .mq5 and an .ex5 file?

An .mq5 file is the source code, which you can read and edit. An .ex5 file is the compiled version that MetaTrader 5 actually runs. Paid EAs almost always come as .ex5, so you cannot see the code. Both belong in the MQL5\Experts folder.