MQL4 and MQL5 are the proprietary programming languages used to build Expert Advisors, custom indicators, and scripts for MetaTrader 4 and MetaTrader 5 respectively. MQL5 is the more modern and capable of the two, supporting more order types and data structures, though the two languages aren't directly cross-compatible.
A large ecosystem of free and paid EAs and indicators exists in both languages, letting traders automate strategies without necessarily writing the code themselves from scratch.
MQL4 & MQL5
The programming languages behind MetaTrader's automated tools — MQL4 for MT4, the more capable MQL5 for MT5.
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