An MQ5 file is a program written for MetaTrader, an online trading platform. It contains source code written in MetaQuotes Language 5 (MQL5), which includes classes, variables, functions, and comments that can be compiled into an .EX5 file. MQ5 files replaced .MQ4 files with the release of MetaTrader 5.

MQ5 files can be opened and edited by MetaEditor, an editor for creating trading robots and technical indicators and included with MetaTrader. MetaEditor can also compile MQ5 files into EX5 Expert Advisor files, which are programs for automating the trading and analytical processes in MetaTrader. The compiling process consists of multiple stages such as a lexical scan, parsing, semantic analysis, code generation, and code optimization. To compile an MQ5, open the source file in "Navigator" and select File → Compile. If there are any errors, the compilation will not be completed no EX5 file will be created. The errors will appear in the "Errors" tab in the "Toolbox" window. MetaTrader software is used for analyzing and trading Stock, Forex, Futures, and CFDs. It comes with technical analysis tools and enables the use of automated trading systems and copy trading.