What Is a Magic Number in MetaTrader?

When an Expert Advisor opens a trade, it can include an integer in the order request — the magic number. The trade server stores that value with the order, copies it onto the resulting position, and keeps it when the trade closes into history. The platform attaches no meaning to it at all: it is a free-form label whose entire job is identification.

Because the value is permanent, a single integer chosen once links every trade a strategy ever makes — which is what makes both automated trade management and per-strategy analytics possible.

A MetaTrader account is a shared space. Manual entries, two or three EAs and the occasional script can all hold positions at the same time, and the position list makes no distinction between them. Yet almost everything an EA does after opening a trade — trailing a stop, scaling out, closing at a session end — starts with scanning that list and asking: which of these are mine?

The magic number — usually combined with the symbol — is that filter. Without it, a trailing-stop routine would happily move stops on trades it never opened, and an “close all my positions” function would flatten the whole account, manual trades included.

The same mechanism works backwards on closed trades. Since each strategy’s trades share a magic number, the account history can be split cleanly into per-strategy groups — no guesswork about which EA produced which result.

Grouped this way, each magic number gets its own profit, win rate, average trade and drawdown instead of one blended account figure. The difference matters: an account that gained 6% over a quarter might hide one EA that made 9% and another that lost 3% — a split that only shows up when trades are grouped by magic number. Which numbers are worth tracking per group is covered in the trading journal metrics guide.

Trades placed by hand — in the desktop terminal, the web platform or the mobile apps — carry magic number 0in both MT4 and MT5. In practice, zero is the de facto “manual” bucket. There are caveats worth knowing:

• Trade panels and one-click scripts count as programs, so anything they open may arrive with its own non-zero magic number even though it felt like a manual entry.
• Some EAs ship with a default magic input of 0 — their trades then land in the manual bucket unless the input is changed.
• Positions closed by the server (a stop-out, for example) keep the magic number of the trade that opened them; closing never re-tags anything.

Any positive integer works; the value comes from consistency. The common convention is one unique number per EA, instrument and version — chosen once, written down, and never reused. Encoding those three parts into the digits keeps the scheme readable at a glance:

Keep values inside the signed 32-bit range (up to 2,147,483,647): MT4 stores the magic as an int, and although MT5 accepts much larger values, staying within MT4’s limit keeps one scheme portable across both platforms. A short note listing which number maps to which EA is worth maintaining — five years of history is only as readable as that mapping.

MetaTrader orders also carry a free-text comment, and it is tempting to use it for identification instead. The two fields behave very differently:

Comments are genuinely useful as notes, but they are not identity. A history export where half the comments read “from #4711022” after partial closes is unusable for grouping — while every one of those trades still carries its original magic number.

Most magic-number problems are invisible while trading and only surface later, when the history no longer splits the way it should:

• Reused numbers. Two EAs sharing a magic number manage each other’s trades and merge into one statistic — the most damaging mistake, and the hardest to untangle afterwards.
• Magic left at 0. The EA’s trades become indistinguishable from manual ones, in management and in analysis alike.
• One number across versions. If version 1 and version 2 share a magic number, a logic change that altered performance is invisible in the grouped results.
• Same EA, several charts, same number. Management usually still works because EAs also filter by symbol, but the statistics for both symbols merge — fine if intended, misleading if not.

A clean magic-number scheme pays off most when comparing a strategy’s live trades against its test results — the subject of why live EA results differ from backtests. You can run that comparison on a Strategy Tester report with the free MetaTrader Backtest Analyzer, and on your own account history with any journal that groups trades by magic number.