MQL5 or MQL4 — which one should your bot be built in?

2 October 2026 · Soft Trade Enterprises · All guides

They are different languages, not two versions of one

This is the single most expensive misunderstanding in this field. MQL4 and MQL5 share a surname and a syntax family, but the order model underneath them is not the same. An MQL4 Expert Advisor cannot be "upgraded" to MQL5 by changing a few function names. In practice a port is a rewrite with the original as a specification.

If you are commissioning new work, decide once, at the start, and build only for that platform.

The order model is the real difference

MQL4 thinks in orders. Every market position and every pending order is an order with a ticket, and you loop through them with OrdersTotal() and OrderSelect().

MQL5 splits that into three separate things:

• Order — a request you sent to the server
• Deal — a transaction that actually executed
• Position — your resulting net exposure in a symbol

That split is why MQL5 code is longer, and also why it is more honest: it tells you what you asked for and what actually happened as two separate facts. Any logic that counts open trades, modifies a stop or closes partially has to be written completely differently.

// MQL4 — one loop over orders
for(int i = OrdersTotal()-1; i >= 0; i--)
{
   if(!OrderSelect(i, SELECT_BY_POS)) continue;
   if(OrderMagicNumber() != MagicNumber) continue;
   // ... act on the order
}

// MQL5 — positions are their own collection
for(int i = PositionsTotal()-1; i >= 0; i--)
{
   ulong ticket = PositionGetTicket(i);
   if(ticket == 0) continue;
   if(PositionGetInteger(POSITION_MAGIC) != MagicNumber) continue;
   // ... act on the position
}

Netting versus hedging

MT5 accounts come in two kinds. On a netting account you hold one position per symbol; a second buy adds to it rather than opening a separate trade. On a hedging account you can hold several independent positions, the way MT4 always worked.

Most retail MT5 accounts in India are hedging accounts, but not all of them, and software written for one behaves incorrectly on the other. This is something worth confirming with your broker before the build starts, not after. We ask for it in the first message for exactly this reason.

What MT5 gives you that MT4 does not

Capability	MT4	MT5
Timeframes available	9	21
Strategy tester	Single-threaded, one symbol	Multi-threaded, multi-symbol, distributed
Real tick history testing	No	Yes, where the broker supplies it
Economic calendar in-terminal	No	Yes, readable from code
Depth of market	No	Yes
Indian exchange segments	Rare	Supported by several brokers
Language features	C-like, limited	Classes, templates, standard library

The multi-symbol tester matters more than people expect. If your rules apply to a basket of symbols, MT4 simply cannot test the basket as one system; you test each symbol separately and the combined exposure stays invisible.

So when is MQL4 still the right answer?

Only two situations, in our experience:

• Your broker offers MT4 and nothing else, and you are not moving brokers.
• You already own working MQL4 source, the logic is not changing, and you only need a small fix. Rewriting it in MQL5 to change ten lines makes no sense.

Everything else — new builds, Indian-market work, anything with a basket, anything you want tested properly — goes to MQL5.

What a migration actually costs

People assume a port is cheaper than a new build. It usually is not. The logic has to be re-derived from code that was written for a different order model, and old MQL4 code is often undocumented. Budget a port at roughly the same as a fresh build, and treat anything cheaper with suspicion.

Where a port is genuinely cheaper is when you hold a clear written specification — then we build from the specification and use the old code only to settle ambiguities.

Before you commission anything

Confirm three things with your broker and have them in writing:

• MT4 or MT5, and whether both are offered on your account type
• Netting or hedging
• The exact symbol names you will trade (they differ between brokers, and hard-coded symbol names are a common cause of a build "not working" after a broker change)

Those three answers decide the platform, and the platform decides everything else.