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Code migration guide

MQL5 to MQL4 converter

Backporting MQL5 to MQL4 can lose capabilities: MQL5 handles, classes, orders, deals, and account-dependent positions must be rewritten for direct indicator calls and the classic MT4 ticket pool.

Open the MQL4 Coding AgentReview MQL4 AI Coding Agent

Generate an MQL4 draft, then compile it in MetaEditor and test it in MetaTrader 4.

Conversion map

What changes between MetaTrader 5 and MetaTrader 4

The migration is a model translation. Use this map to decide where the source behavior belongs before writing target syntax.

Source and target platform conversion map
ConcernSource modelTarget modelMigration decision
LifecyclePrograms respond to typed events such as OnInit, OnTick, OnTradeTransaction, and OnCalculate.Expert Advisors and indicators respond to predefined callbacks such as OnInit, OnTick, and OnCalculate.Choose when each MetaTrader 5 calculation should run in MetaTrader 4; matching syntax alone does not preserve timing.
Market data and historyTimeseries and indicator values are commonly copied into arrays; built-in indicators return handles read with CopyBuffer.Price series use terminal arrays and shift-based access; indicators commonly expose calculated values through buffers.Recheck bar indexing, warm-up requirements, timeframe requests, and behavior on an unfinished bar.
Indicators and chart outputIndicator handles, buffers, plots, and OnCalculate separate setup from repeated calculation.Custom indicators bind buffers, while built-in indicator functions can return values directly for a requested shift.Map calculations before recreating plots, labels, colors, and platform-specific drawing objects.
Orders and positionsTrade requests and CTrade operate with orders, deals, and account-dependent position models.Classic trade functions such as OrderSend work with order tickets, lots, prices, stops, and a shared order pool.Define fill timing, sizing, pyramiding or hedging, stops, and position ownership for the target platform.
Native validationCompile the .mq5 file in MetaEditor 5, load it in MetaTrader 5, and use Strategy Tester for the intended artifact.Compile the .mq4 file in MetaEditor, attach it in MetaTrader 4, and test the correct EA or indicator artifact.Treat generated MQL4 as a draft until it passes the target editor, chart, and backtest workflow.

Code example

Moving-average cross: MQL5 to MQL4

These fragments show where the same signal starts in each API. They are not complete standalone programs; lifecycle setup, inputs, plots, and order handling still depend on the selected artifact.

MQL5 source fragment
double fast[2], slow[2];
CopyBuffer(fastHandle, 0, 0, 2, fast);
CopyBuffer(slowHandle, 0, 0, 2, slow);
bool longSignal = fast[0] <= slow[0] && fast[1] > slow[1];
MQL4 target fragment
double fast0 = iMA(NULL, 0, 10, 0, MODE_SMA, PRICE_CLOSE, 0);
double fast1 = iMA(NULL, 0, 10, 0, MODE_SMA, PRICE_CLOSE, 1);
double slow0 = iMA(NULL, 0, 20, 0, MODE_SMA, PRICE_CLOSE, 0);
double slow1 = iMA(NULL, 0, 20, 0, MODE_SMA, PRICE_CLOSE, 1);
bool longSignal = fast1 <= slow1 && fast0 > slow0;

Workflow

A four-step migration path

Keep generation, target-platform validation, and behavior comparison as separate stages.

  1. 1

    Inventory the source behavior

    Separate calculations, plots, alerts, orders, external dependencies, and assumptions in an .mq5 Expert Advisor or custom indicator.

  2. 2

    Choose the target artifact

    Decide whether the result is an .mq4 Expert Advisor or custom indicator. This choice controls lifecycle methods and available APIs.

  3. 3

    Rewrite through target APIs

    Translate state, series, indicators, drawings, and orders into MetaTrader 4 concepts instead of replacing function names.

  4. 4

    Validate behavior natively

    Compile the .mq4 file in MetaEditor, attach it in MetaTrader 4, and test the correct EA or indicator artifact.

Manual decisions

Decisions code replacement cannot make

  • Replace MQL5 indicator handles and CopyBuffer access with MQL4 calls or custom buffers.
  • Flatten unsupported library or language features while keeping ownership and cleanup explicit.
  • Define how MT5 netting or hedging positions map to independent MT4 order tickets.

Limitations

What the draft cannot prove

  • MetaTrader 5 and MetaTrader 4 do not share one execution, data, or order model, so behavior can change even when both versions compile.
  • Broker, symbol, session, timezone, history, and fill settings can change signals and backtest results on MetaTrader 4.
  • Pineify can generate and revise a MQL4 draft, but the target platform remains the authority for compilation, loading, backtesting, and runtime behavior.

Use cases

When this conversion is useful

  • Backport an MT5 Expert Advisor for an MT4-only broker environment.
  • Rebuild an MQL5 indicator with MQL4-compatible buffers and calls.
  • Identify MT5-only features before committing to a reduced MT4 implementation.

FAQ

MQL5 to MQL4 questions

Official references

Build the MQL4 draft with its native model in view

Bring the complete source and your artifact, timing, data, and order requirements. Validate the result in MetaTrader 4.

Open the MQL4 Coding AgentProduct details