Why XAUUSD for an Expert Advisor

• Gold traded a reported average of US$361bn a day in 2025, most of it over the counter in London.
• Its trading day is nearly continuous but not quite: the COMEX futures session breaks for an hour each afternoon.
• Spread on XAUUSD is set by your broker, not an exchange — which is why a backtest’s spread setting decides so much.

“Why gold?” deserves a better answer than “it moves a lot”. Four properties of the XAUUSD market decide whether a strategy can be automated on it at all, and each of them is a fact you can check rather than a preference.

Liquidity

Gold is one of the most heavily traded assets there is. The World Gold Council reports that gold’s overall trading volumes averaged approximately US$361bn per day in 2025, split between about US$180bn a day over the counter — mostly spot, mostly London — US$174bn a day in futures across global exchanges, and around US$7bn a day in gold ETFs (World Gold Council). The same source notes that the gold market is more liquid than several major assets, including euro/sterling and the Dow Jones Industrial Average, and that gold’s liquidity “does not dry up, even at times of financial stress”.

For an Expert Advisor this is the property that matters most, and it is easy to under-rate. Liquidity is what makes a modelled fill in a backtest resemble a real one. On a thin instrument the tester’s assumption that your order filled at the price it saw is fiction; on gold it is at least a defensible approximation most of the time.

The trading day, and the hole in it

Gold trades nearly around the clock, and the exact shape of the day is published rather than folklore.

The benchmark LBMA Gold Price is set twice each business day, at 10:30 and 15:00 London time, in US dollars per troy ounce, in electronic auctions administered by ICE Benchmark Administration (LBMA). Both fall inside London hours, and the afternoon one inside the window when London and New York are open together.

COMEX gold futures (GC) trade on CME Globex Sunday through Friday from 5:00 p.m. to 4:00 p.m. Central Time, with a 60-minute break (CME Group). That hour is the closest thing gold has to a nightly close. What your own broker’s spot XAUUSD feed does during it is a question for that broker’s contract specification rather than for us — check it before you let a strategy trade through it.

Two consequences for an automated strategy. First, a strategy that trades a named session needs its broker’s server time handled correctly, including daylight-saving changes, or its window drifts by an hour twice a year. Second, the daily break is exactly the sort of hour where a fixed backtest spread stops resembling anything.

Volatility

Gold moves enough to be worth trading, and its volatility is published rather than guessed at: the World Gold Council maintains the rolling annualised series and a comparison against other asset classes (World Gold Council). Read it there rather than taking a number from us — this page carries no figure we have not linked.

Two things follow. Gold gives a trend-follower or a breakout strategy moves large enough to pay for the false starts — that is the case for it. And gold’s volatility is not constant, which is the case for caution: a strategy whose position size, stop distance or channel width was fitted to one volatility regime behaves differently in another, and will not tell you it has changed.

This is also why the size of a strategy’s worst drawdown is the number to test against several years rather than one.

Spread, and why it is your broker’s decision

XAUUSD as your broker quotes it is not an exchange product. There is no central book you are trading against and no exchange-set spread. Your broker sets the quote, the spread, the contract size and the swap, and publishes them in the symbol’s contract specification inside MetaTrader 5 — which is also where the Strategy Tester reads them from (MetaTrader 5 Help).

Three practical consequences:

• Two brokers are two instruments. XAUUSD, XAUUSD+ and XAUUSD.a have different spreads, different tick histories and sometimes different contract sizes. A result from one does not transfer to another.
• The tester’s spread setting is a decision, not a detail. Choosing “current spread” at a quiet moment bakes a calm market into an entire run.
• Commission is separate and often uncharged in testing. On the feed our own desk tested, the MetaTrader 5 tester charged nothing per lot on XAUUSD while real trading on the same instrument cost roughly $7 per lot round-turn — a gap large enough to change a conclusion.

So: is XAUUSD a good instrument to automate?

It is a defensible one. It is deeply liquid, its trading calendar is documented, its volatility is large enough to matter and it is available on essentially every MetaTrader 5 broker, which is why so much retail automation is written for it.

None of that is an edge. Liquidity and long hours make a strategy testable; they do not make it profitable, and gold’s leverage cuts in both directions with the same enthusiasm.

The way to find out is to run it yourself, on your own broker’s ticks, over more than one year — how to backtest a gold EA in MT5 covers the settings that decide whether that run means anything.

Before you act on any of this

Every figure XauStack publishes comes from the MetaTrader 5 Strategy Tester, never from live trading, and no result is promised anywhere on this site. Trading gold on leverage carries a high risk of losing money rapidly, and depending on your broker and jurisdiction you can lose more than you deposit. Read the risk disclosure before you trade it, automated or otherwise.