Use a trusted, open-source EX4 decompiler from GitHub on a disconnected virtual machine after scanning for viruses. Accept that the output code will be ugly but functional.
Instead of chasing the fantasy of free decompilation, follow this practical action plan: how to convert ex4 to mq4 free work
Converting an file (compiled executable) back into an MQ4 file (source code) for free is extremely difficult and often impossible for modern versions of MetaTrader 4. While older versions of MQL4 (pre-2014) used bytecode that was easily reversible, modern versions (Build 600+) utilize machine code and encryption, making them virtually "un-decompilable" for the average user. The Reality of "Free" Decompilers Use a trusted, open-source EX4 decompiler from GitHub
Call that value in your new code without needing to convert the file. 5. Last Resort Options Ex4 To Mq4 Decompiler 4.0.432 | Updated - Google Groups While older versions of MQL4 (pre-2014) used bytecode