List of Real-Time Operating Systems

List of Real-Time Operating Systems (RTOS)

S. No.	Operating System	Developer / Origin	Category / Features / Status
1	FreeRTOS	Amazon Web Services / open-source community	Lightweight, open-source RTOS for microcontrollers, IoT devices, sensors and embedded systems. Actively maintained.
2	Zephyr RTOS	Linux Foundation ecosystem	Open-source RTOS for connected devices, wearables, embedded controllers and IoT hardware. Actively developed.
3	QNX Neutrino	BlackBerry, Canada	Commercial microkernel RTOS used in automotive systems, industrial automation and safety-critical applications.
4	VxWorks	Wind River	Commercial RTOS used in aerospace, defence, robotics, industrial equipment and mission-critical embedded systems.
5	ThreadX	Microsoft / Azure RTOS ecosystem	Compact RTOS for microcontrollers and embedded devices. Now associated with the Eclipse ThreadX project.
6	SafeRTOS	WITTENSTEIN high integrity systems	Safety-oriented RTOS designed for embedded applications requiring rigorous safety processes.
7	INTEGRITY	Green Hills Software	Commercial real-time operating system emphasizing security, isolation and safety-critical operation.
8	RTEMS	RTEMS Project	Open-source RTOS used in aerospace, spaceflight, scientific instruments, telecommunications and embedded systems.
9	embOS	SEGGER Microcontroller	Compact commercial RTOS for microcontrollers, industrial equipment and embedded products.
10	CMSIS-RTX	Arm ecosystem	RTOS implementation supporting the CMSIS-RTOS API for Arm Cortex-M embedded applications.
11	µC/OS-II	Originally Micrium	Compact, priority-based RTOS used in embedded systems and educational projects; a legacy product family.
12	µC/OS-III	Originally Micrium	Multitasking RTOS for embedded controllers, offering task scheduling, synchronization and inter-task communication.
13	TI-RTOS	Texas Instruments	Embedded RTOS ecosystem for selected TI microcontrollers and processors; product offerings have evolved into newer SDKs and kernels.
14	SYS/BIOS	Texas Instruments	Real-time kernel used in TI embedded development environments, particularly for supported DSP and microcontroller platforms.
15	Nucleus RTOS	Originally Mentor Graphics	Commercial embedded RTOS family used in networking, consumer electronics and industrial devices.
16	Deos	DDC-I	Safety-critical RTOS designed for aerospace and other high-assurance embedded applications.
17	PikeOS	SYSGO	Real-time operating system and separation-kernel platform for avionics, rail, automotive and industrial systems.
18	LynxOS	Lynx Software Technologies	Unix-like real-time operating system used in defence, aerospace, industrial and mission-critical applications.
19	LynxOS-178	Lynx Software Technologies	Safety-oriented RTOS platform designed for avionics and applications requiring stringent certification.
20	ERIKA Enterprise	ERIKA community / Evidence	Automotive-oriented RTOS designed for embedded control applications and supported microcontroller platforms.
21	ChibiOS/RT	ChibiOS community	Compact RTOS and embedded development framework used with microcontrollers, including STM32 devices.
22	RT-Thread	RT-Thread community	Open-source RTOS with device drivers, networking components and software packages for embedded and IoT devices.
23	NuttX	Apache Software Foundation	Open-source RTOS offering POSIX-oriented interfaces for embedded controllers, robotics and connected devices.
24	Apache Mynewt	Apache Software Foundation	Open-source embedded operating system designed for resource-constrained devices, particularly connected and Bluetooth-enabled hardware.
25	Contiki-NG	Open-source community	Operating system for low-power IoT devices and wireless sensor networks.
26	RIOT OS	RIOT community	Open-source operating system for low-power IoT devices, networked sensors and constrained embedded hardware.
27	Zephyr-based embedded systems	Zephyr community and hardware vendors	Device-specific embedded platforms built using Zephyr components; these are implementations rather than separate RTOS kernels.
28	eCos	Originally Red Hat; community-supported	Configurable open-source RTOS designed for embedded applications with limited hardware resources.
29	embOS-Ultra	SEGGER Microcontroller	High-performance RTOS variant intended for applications requiring efficient scheduling and precise timing.
30	Keil RTX5	Arm ecosystem	RTOS kernel for Arm Cortex-M microcontrollers with CMSIS-RTOS2 support.
31	Azure RTOS ThreadX	Originally Microsoft / Express Logic	Historical product name for the ThreadX RTOS family; related development continues under Eclipse ThreadX.
32	OSE	Enea, Sweden	Commercial real-time operating system historically used in telecommunications, networking and embedded systems.
33	OSEK/VDX OS	Automotive industry consortium	Automotive operating-system standard for predictable embedded control. Implementations provide real-time scheduling.
34	AUTOSAR Classic OS	AUTOSAR partnership	Automotive operating-system architecture for electronic control units, supporting deterministic task scheduling and standardized interfaces.
35	Trampoline RTOS	Open-source community	Automotive-oriented RTOS implementation based on OSEK/VDX and AUTOSAR concepts.
36	SCIOPTA	SCIOPTA Systems	Commercial RTOS for embedded applications, including industrial control and systems with strict timing requirements.
37	INTEGRITY-178 tuMP	Green Hills Software	Safety-critical multicore operating-system platform for avionics and other high-assurance applications.
38	Deos Multicore	DDC-I	Multicore-capable safety-critical RTOS platform designed for aerospace applications.
39	VRTX	Originally Ready Systems	Historical commercial RTOS family used in embedded controllers and industrial systems.
40	pSOS	Originally Integrated Systems	Historical RTOS used in networking equipment, telecommunications and embedded products.
41	OS-9	Microware / later Radisys	Modular real-time operating system used in industrial systems, embedded computing and legacy control equipment.
42	PDOS	Historical embedded computing ecosystem	A name used for multiple systems; not a single widely standardized modern RTOS. Specific implementations require identification.
43	FreeOSEK	Open-source community	Historical open-source OSEK/VDX-compatible automotive RTOS implementation.
44	µITRON	TRON ecosystem, Japan	Real-time operating-system specification widely used in Japanese embedded systems; multiple implementations exist.
45	T-Kernel	T-Engine Forum / TRON ecosystem	Real-time kernel architecture for embedded systems and electronic devices.
46	TOPPERS/ASP	TOPPERS Project, Japan	Open-source RTOS implementation based on embedded real-time kernel specifications.
47	TOPPERS/FMP	TOPPERS Project, Japan	Multiprocessor-oriented RTOS implementation for supported embedded systems.
48	MQX RTOS	Originally Precise Software Solutions; later Freescale / NXP ecosystem	Embedded RTOS family historically used in industrial equipment, networking and microcontroller applications.
49	Thread-M	Historical embedded RTOS naming	The name is not sufficiently standardized to identify one major current RTOS confidently; verify the specific vendor or implementation.
50	RTLinux	Originally FSMLabs	Real-time Linux technology that combines Linux with real-time execution mechanisms; the original product differs from PREEMPT_RT Linux.
51	PREEMPT_RT Linux	Linux kernel community	Linux kernel real-time preemption support for reducing scheduling latency; not a separate standalone RTOS distribution.
52	Xenomai	Xenomai community	Real-time framework for Linux-based systems, providing real-time interfaces and execution capabilities for supported hardware.
53	RTAI	RTAI community	Real-time application interface for Linux, used in industrial control, robotics and research.
54	RT-Thread Smart	RT-Thread community	RT-Thread-related operating-system environment for more capable embedded processors; architecture and configuration differ from its microcontroller RTOS.
55	ChorusOS	Originally Chorus Systèmes / Sun Microsystems	Historical real-time operating system designed for distributed embedded and telecommunications systems.
56	VRTXsa	Historical commercial RTOS ecosystem	Variant associated with the legacy VRTX operating-system family for embedded applications.
57	CMX-RTX	Originally CMX Systems	Historical commercial RTOS for microcontrollers and embedded products.
58	embOS-MPU	SEGGER Microcontroller	embOS variant providing memory-protection support on suitable processor architectures.
59	uC/OS-III-based systems	Micrium ecosystem	Embedded products built around the µC/OS-III kernel; not a distinct kernel from µC/OS-III itself.
60	FreeRTOS SMP	Amazon Web Services / FreeRTOS community	Symmetric multiprocessing support within FreeRTOS for supported multicore processors and configurations.

Notes:

An RTOS prioritizes predictable response times and task deadlines, not simply maximum processing speed.
Hard real-time: missing a deadline can cause system failure or unacceptable consequences. Soft real-time: occasional deadline misses degrade performance but may be tolerable.
FreeRTOS, Zephyr, RTEMS, RT-Thread and NuttX are notable open-source choices. QNX Neutrino, VxWorks, INTEGRITY and PikeOS are examples of commercial platforms.
Not every RTOS is suitable for safety-critical applications. Certification, processor support, scheduling behavior and the complete system design must be evaluated for the intended use.
PREEMPT_RT Linux, Xenomai and RTAI are real-time Linux approaches or frameworks, not all independent standalone operating systems.
Some entries are historical systems, product variants, standards or implementation families rather than distinct RTOS kernels. They are identified accordingly.
This list contains 60 entries, but it is not a list of 60 entirely independent operating-system kernels.

Official references:

List of Real-Time Operating Systems

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