What Is MQL5? Programs, Events, and a First MT5 Workflow
MQL5 is MetaQuotes' programming language for MetaTrader 5. It supports custom indicators, Expert Advisors, scripts, services, and reusable code. Automation executes the rules you implement; it does not establish that those rules are profitable or that every order will succeed.
Choose the right program type
An Expert Advisor can respond to events and submit trade requests. A custom indicator calculates analytical outputs rather than placing trades automatically. A script runs through its start handler for a task; a service can run independently of a chart. Libraries and include files provide reusable functionality. The MQL5 reference documents these distinctions.
Keep human-readable .mq5 source and any included files. Compilation produces an .ex5 executable, which is not a substitute for your editable source. For readable learning examples, use the official CodeBase and check their licenses; a Market download is not necessarily distributed with source.
Understand the event model
OnInit() initializes an attached EA and can run again after reinitialization. OnDeinit() handles cleanup. OnTick() responds to new-tick events for the attached chart's symbol; it is not a callback for every price change on every instrument. If a NewTick event is already queued or being processed, another is not added to the queue. See the official OnTick documentation.
Other handlers can respond to timers and trade transactions. Multi-symbol logic therefore needs an explicit scheduling and data-access design. OnTester() can return a custom optimization criterion after a test; it is not the only way to obtain tester statistics.
An EA requires an operating terminal or suitable hosting, connectivity, permissions, and available market sessions. Broker restrictions, invalid requests, or disconnections can prevent execution. “Set and forget” and “never miss a signal” are unsuitable guarantees.
MQL5 and MQL4
Both languages support object-oriented programming; MQL4's own reference documents classes and inheritance. MQL4 is not restricted to one traded symbol per EA. Migration still requires attention to indicator handles, trading APIs, and the distinction between orders, deals, and positions.
MT5 account configuration determines netting or hedging behavior. Depth-of-market availability depends on the instrument and broker; it is not universally complete. MT5's tester supports multi-currency testing and optimization agents, but that does not prove an arbitrary test finishes a particular number of times faster. See the Strategy Tester overview.
Build and evaluate a small EA
- Install MT5 from MetaQuotes or your intended broker and open MetaEditor.
- Create an Expert Advisor template and define inputs, signal timing, order sizing, and error handling.
- Compile and resolve errors. Review warnings rather than treating a generated executable as proof of correct behavior.
- Backtest with an appropriate data/modeling mode, costs, and a recorded parameter set. Reserve a separate period for evaluation.
- Forward-test on a demo account. Check logs, duplicate orders, rejected requests, and reconnect behavior before considering live execution.
The previous four-hour build, 1.8 profit factor, and 50-orders-per-second claims are not supported by an attached test record.
Pineify's MQL5 Coding Agent can assist with drafting and revising code. Evaluate its output through the same compiler and testing workflow. This page does not establish proprietary training data, a guaranteed error-free result, or a measured advantage over generic assistants.
