MetaTrader 4, also known as MT4, is an electronic trading platform widely used by online retail foreign exchange speculative traders. It was developed by MetaQuotes Software and released in 2005. The software is licensed to foreign exchange brokers who provide the software to their clients. The software consists of both a client and server component. The server component is run by the broker and the client software is provided to the broker’s customers, who use it to see live streaming prices and charts, to place orders, and to manage their accounts.

The client is a Microsoft Windows-based application that became popular mainly due to the ability for end users to write their own trading scripts and robots that could automate trading. In 2010 MetaQuotes released a successor, MetaTrader 5, however uptake was slow and as of April 2013 most brokers still used MT4. While there is no official MetaTrader 4 version available for Mac OS, some brokers provide their own custom developed MT4 variants for Mac OS.