ReactOS主要是由C语言编写。部分元件则由C++编写，例如ReactOS文件浏览器。
为确保操作系统没有任何一部份是看过泄漏出来的 Microsoft 源码的人所写，或者逆向工程的过程达不到 Clean room design 标准，一个全盘的源码审查由 ReactOS 主要开发者下令展开。此审查现正与 ReactOS 的开发同步进行中。* Freeldr was improved
* HAL's key areas have been significantly improved (irql-related, bus support, kd-functions)
* The Kernel experienced a massive rewrite of incompatible parts (and is still in the process of improvement)
* Run-time library (Rtl) got a lot of improvements and bugfixes
* Bugs were fixed in kernel-mode drivers and a better USB driver was added
* Registry-support has been greatly improved thanks to addition of "cmlib", a library shared by the boot loader and the kernel to handle binary registry hives; it even supports binary registry hives created by Windows
* More fixes in the Win32 subsystem and user-mode DLLs
* Boot video driver (and a splash screen) was added
访问:ReactOS 0.3.1