MQL4 vs MQL5: Why Your Expert Advisors Won’t Cross Over (and What You Can Actually Do About It)

So here’s a question I hear almost weekly from traders: I’ve got this great EA running on MT4—can I just drop it into MT5 and keep going?

The short answer is no. But the longer answer is far more interesting—and more useful if you’re trying to figure out what to do next.

The Core Incompatibility Isn’t a Bug—It’s a Fundamental Redesign

When MetaQuotes built MQL5, they didn’t just update the language. They rebuilt it from the ground up. MQL4 was designed for simplicity—procedural, straightforward, and tightly coupled with MT4’s order management system . MQL5, on the other hand, is a fully object-oriented language closer to C++, with native x64 compilation and a completely different architecture for handling orders and positions .

What does this mean in practice?

• MQL4 manages individual orders. Every trade is a standalone entry. Open three Buy trades on EURUSD? That’s three separate orders.
• MQL5 distinguishes between orders, deals, and positions. In netting mode, multiple entries on the same symbol merge into a single position . This changes everything—how you track open trades, how you calculate profit, and how you close them.

So if your MT4 EA uses OrderSelect(), OrderSend(), or loops through OrdersTotal() expecting a list of individual trades, it won’t even compile in MT5. And the trading functions—the core logic of your EA—are the hardest part to translate .

The Migration Headache: What Actually Changes

Let’s get specific. Here are the biggest pain points when moving MQL4 code to MQL5:

1. Order handling becomes position handling – In MQL4, you manage each trade independently. In MQL5, OrdersTotal() only returns pending orders, while PositionsTotal() gives you open positions. They’re separate functions now . If your code assumes they’re the same, you’re in for a long debugging session.

2. Indicator logic is completely different – MQL4 uses a “call and get” approach. iMA(NULL, 0, 14, 0, MODE_SMA, PRICE_CLOSE, 1) gives you a value immediately. In MQL5, you create an indicator handle, then use CopyBuffer() to pull data into an array . It’s more efficient—MQL5 caches indicator calculations so you’re not recalculating on every tick—but it requires rewriting your entire indicator logic .

3. The event model changes – MQL4 relies heavily on start() or OnTick(). MQL5 introduces OnTimer(), OnTrade(), OnChartEvent(), and more . This gives you finer control, but it means your EA’s structure has to change.

4. Built‑in variables vanish – Bid, Ask, Time[], Close[]—these don’t exist in MQL5. You have to use SymbolInfoDouble() and CopyRates() .

Why Bother Migrating at All?

If the migration is this much work, why not just stick with MT4?

Because MQL5 delivers serious performance advantages :

• Speed: MQL5 runs 4 to 20 times faster than MQL4, approaching C++ performance .
• Multi‑threaded backtesting: The strategy tester uses multi‑core CPUs and the MQL5 Cloud Network to run complex optimizations in minutes instead of days .
• More timeframes: 21 vs. MT4’s 9 .
• Depth of Market (DOM): Available in MT5, not in MT4 .
• Ongoing development: MetaQuotes has stopped major updates to MT4. MT5 is the future .

So the trade‑off is clear: you put in the migration effort now, or you stay on a platform that’s functionally frozen.

A Practical Reality Check: You Might Not Need to Choose

Here’s where the conversation gets interesting.

Even if you’re migrating to MQL5 or maintaining both platforms, there’s still a day‑to‑day workflow problem that neither language solves: you have to keep the platform open to see what’s happening with your trades.

If you’re running EAs in the background, you’re probably leaving MT4 or MT5 open all day. The chart windows clutter your screen, the terminal window sits in your taskbar, and you keep alt‑tabbing back to check if your positions are still running.

This is where the workflow question becomes: how do I keep an eye on my EAs without keeping the whole platform in my face?

Camovia Tray addresses this exact friction point. It turns MT5 or MT4 into a system tray tool—you can check live quotes by hovering over the tray icon, and view your open positions (symbol, direction, volume, entry price, current P&L) without opening the terminal [citation:1 in knowledge base]. The data is read directly from your local terminal and never leaves your computer [citation:1 in knowledge base].

If you’re testing a migrated EA on MT5 while still running an older one on MT4, you can switch data sources in the settings—it automatically cleans up the previous terminal connection [citation:1 in knowledge base]. And if you need to close a position quickly, you can do it from the order card with a two‑step confirmation [citation:1 in knowledge base].

The point isn’t that Camovia Tray replaces MQL5 or makes migration easier—that’s a code problem, not a UI problem. The point is that once you’ve made the migration or you’re managing both platforms, you still need a way to monitor what’s happening without keeping the entire trading platform front and center all day. The tool puts your positions and quotes in the system tray, lets you hide the main window (it disappears from the taskbar and Alt+Tab), and gives you privacy features like tray icon camouflage and a privacy lock [citation:1 in knowledge base].

The Bottom Line

MQL4 and MQL5 are not compatible, and they’re not meant to be. The migration isn’t a find‑and‑replace exercise—it’s a rewrite that forces you to understand the underlying architecture differences. But if you’re going to make the move, you’re gaining a faster, more capable platform that’s still being actively developed.

And in the meantime, whether you’re on MT4, MT5, or both, the daily challenge remains: how do I monitor my positions without living inside the terminal? That’s a question about workflow, not code—and it’s one worth solving no matter which version of MQL you end up writing.