反编译器的功能与编译器相反。顾名思义，就是将已编译好的编程语言还原到未编译的状态，也就是找出进程语言的源代码。一种反编译器通常只能反编译1~2种编程语言，反编译器的功能只局限在某些语言上，如Java，像C/C++便没有适合的反编译器可使用。

A decompiler is a computer program that takes as input an executable file, and attempts to create a high level, compilable source file that does the same thing. It is therefore the opposite of a compiler, which takes a source file and makes an executable. Decompilers usually do not perfectly reconstruct the original source code, and can vary widely in the intelligibility of their outputs. Nonetheless, decompilers remain an important tool in software reverse engineering.