MQL5 vs MQL4. Which one?
A clear comparison of the two MetaTrader languages, from paradigm and performance to the order model, so you know which to build your Expert Advisor in.
ZENKEI
ZENKEI
A clear comparison of the two MetaTrader languages, from paradigm and performance to the order model, so you know which to build your Expert Advisor in.
MQL5 is the newer, object-oriented language for MetaTrader 5: faster, built for complex systems, with a position-based order model and multi-currency backtesting. MQL4 is the older, procedural language for MetaTrader 4, simpler and backed by a huge legacy codebase. For new development, code in MQL5. Choose MQL4 only when you must target MetaTrader 4 or maintain existing MQL4 code. The two are separate languages, so code does not port automatically.
MQL4 and MQL5 are the programming languages behind MetaTrader 4 and 5. They look similar on the surface, and a 2014 update brought their syntax closer, but they differ in paradigm, performance and, most importantly, how they handle orders. Here is the comparison that matters for building an Expert Advisor or indicator.
| Aspect | MQL4 | MQL5 |
|---|---|---|
| Platform | MetaTrader 4 | MetaTrader 5 |
| Paradigm | Procedural | Object-oriented, close to C++ |
| Performance | Fast enough | Faster, 64-bit compiled |
| Order model | Order-based, simple functions | Position-based, trade request structures |
| Classes & structures | Limited | Full support, plus a Standard Library |
| Indicators | Straightforward, fewer buffers | More flexible, more buffers |
| Backtesting | Single-symbol | Multi-currency, real ticks |
| Learning curve | Gentler | Slightly steeper, cleaner at scale |
| Legacy code | Very large | Growing |
| Best for | Maintaining MT4 systems | New projects and complex systems |
MQL4 is the procedural language of MetaTrader 4. Its order functions are simple and its structure is easy to pick up, which is a big reason MT4 became the retail standard. The trade-off is that large, complex systems get unwieldy without classes, and it is tied to a platform many brokers are gradually moving away from. Its biggest asset today is the enormous library of existing MQL4 Expert Advisors and indicators.
MQL5 is the object-oriented language of MetaTrader 5, with syntax close to C++. It supports classes, structures and pointers, ships with a Standard Library of ready-made trading classes, and compiles to faster 64-bit code. Its order model is position-based and more explicit, which takes a little more code but scales cleanly to complex, multi-instrument systems. If you are building something new, MQL5 is the more future-proof choice.
The change that trips up most people moving between the two is not syntax, it is how trades work. MQL4 thinks in individual orders with tickets and uses simple calls to open and close them. MQL5 thinks in positions and uses trade request structures, or the Standard Library trade classes, to manage them. This is why MQL4 code cannot simply run on MQL5: the underlying trading logic is modelled differently.
Because they are separate languages, moving an Expert Advisor from MQL4 to MQL5 means rewriting it, not recompiling it. The strategy logic carries over, but the order handling has to be rebuilt around MQL5's position model. It is a routine job for a developer, and a good moment to tidy up old code and add MT5-only features. We offer this directly as an MQL4 to MQL5 conversion, alongside our MQL5 programming and Expert Advisor development services.
Whether you are starting fresh in MQL5 or moving an MQL4 system across, we can help. See our MQL5 programming and Expert Advisor development services, or learn how an EA is built.
MQL4 is the older, procedural language for MetaTrader 4, while MQL5 is the newer, object-oriented language for MetaTrader 5. MQL5 is faster, supports classes, structures and pointers, uses a position-based order model, and its Strategy Tester runs multi-currency backtests.
For new development, yes. MQL5 is faster, more capable and object-oriented, and runs on MetaTrader 5, the platform most brokers are moving to. MQL4 is only preferable when you must target MetaTrader 4 or maintain existing MQL4 code.
No. MQL4 and MQL5 are separate languages with different order models, so MQL4 code does not run on MetaTrader 5. Moving a strategy across means rewriting it in MQL5, a routine conversion for a developer.
MQL5 has a slightly steeper start because it is object-oriented and its order model is more explicit, but it is cleaner for complex systems. Since a 2014 update the two share much of their syntax, so the jump is smaller than it used to be.
Learn MQL5 if you are starting now: it is current, more powerful and future-proof. Learn MQL4 only if you specifically need to maintain existing MetaTrader 4 Expert Advisors or indicators.
Bring your strategy or your existing code. We build it, or port it, source code included.