List of open source real-time operating systems.

Name License Description Version Links Last updated
FreeRTOS Modified GPL MSP430 ARM AVR ColdFire PIC x86 FreeRTOS is a popular real-time operating system for embedded devices, being ported to 31 microcontrollers. It is distributed under the GPL with an optional exception. V9.0.0 Code 2016-05-26
RT-Thread GPL x86 MIPS PowerPC RT-Thread is an open source real-time operating system for embedded devices from China. RT-Thread RTOS is a scalable real-time operating system: a tiny kernel for ARM Cortex-M0, Cortex-M3/4, or a full feature system in ARM Cortex-A8, ARM Cortex-A9 DualCor v2.1.0 GitHub 2016-04-24
Contiki OS BSD MSP430 ARM AVR 8051 Contiki is an open source operating system for the Internet of Things. Contiki connects tiny low-cost, low-power microcontrollers to the Internet. 3.0 GitHub 2015-08-24
mbed OS Apache License ARM mbed OS is an open-source embedded operating system designed specifically for the "things" in the Internet of Things (IoT). It includes all the features you need to develop a connected product based on an ARM Cortex-M microcontroller. 5.1 GitHub 2016-09-17
ChibiOS/RT Modified GPL MSP430 AVR ChibiOS is a complete development environment for embedded applications including RTOS, an HAL, peripheral drivers, support files and a development environment. 17.6.0 Code 2017-06-04
NuttX BSD ARM AVR 8051 x86 NuttX is a real-time operating system (RTOS) with an emphasis on standards compliance and small footprint. Scalable from 8-bit to 32-bit microcontroller environments, the primary governing standards in NuttX are Posix and ANSI standards. 7.21 Code 2017-06-16
RIOT LGPLv2.1 MSP430 AVR RIOT is a real-time multi-threading operating system that supports a range of devices that are typically found in the Internet of Things (IoT): 8-bit, 16-bit and 32-bit microcontrollers. 2017.04 GitHub 2017-05-10
RTEMS GPL ARM x86 MIPS PowerPC m68k RTEMS is an open source RTOS that supports open standard application programming interfaces such as POSIX. It is used in space flight, medical, networking and many more embedded devices. 4.11 Code 2016-09-23
Apache Mynewt Apache License ARM Apache Mynewt OS is a real-time, modular operating system for connected IoT devices that need to operate for long periods of time under power, memory, and storage constraints. It provides a complete environment for prototyping, developing, and managing em pre_sterly_refactor GitHub 2016-09-21
RTAI GPL ARM x86 PowerPC x86_64 m68k RTAI is the RealTime Application Interface for Linux - which lets you write applications with strict timing constraints for your favourite operating system. The RTAI distribution includes RTAI-Lab, a tool chain to convert block diagrams into RTAI executab RTAI 5.0-test1 Code 2015-12-06
Xenomai GPL ARM x86 PowerPC Xenomai is a real-time development framework cooperating with the Linux kernel, in order to provide a pervasive, interface-agnostic, hard real-time support to user-space applications, seamlessly integrated into the GNU/Linux environment. v3.0.3 Code 2016-09-10
Atomthreads BSD AVR Atomthreads is a free, lightweight, portable, real-time scheduler for embedded systems. release1.3 GitHub 2017-05-23
StratifyOS GPL ARM StratifyOS is a powerful embedded RTOS for the ARM Cortex M microcontrollers. v2.2.0 GitHub 2017-04-10
distortos Mozilla Public License Version 2.0 ARM Distortos is an advanced RTOS written in C++11. v0.4.0 GitHub 2017-03-11
Zephyr Apache License ARM x86 The Zephyr™ Project is a scalable, real-time operating system (RTOS) supporting multiple hardware architectures, optimized for resource constrained devices, and built with security in mind. This Linux Foundation hosted project embraces open source development values and governance on its mission to unite leaders from across the industry to produce a best-in-breed solution. zephyr-v1.8.0 GitHub 2017-06-15
StateOS GPL v3 ARM Free, extremely simple and amazingly tiny real-time operating system (RTOS) designed for deeply embedded applications. Target: ARM Cortex-M family. It was inspired by the concept of a state machine. v4.9 GitHub 2017-06-13
F9 Microkernel BSD ARM F9 microkernel is a microkernel-based (L4-style) kernel to support running real-time and time-sharing applications (for example, wireless communications) for ARM Cortex-M series microprocessors with efficiency (performance + power consumption) and security (memory protection + isolated execution) in mind. GitHub 2017-02-01
BRTOS MIT MSP430 AVR ColdFire PIC BRTOS is a lightweight preemptive real time operating system designed for low end microcontrollers. GitHub 2017-05-22
BeRTOS Modified GPL AVR x86 PowerPC x86_64 BeRTOS is a real time open source operating system supplied with drivers and libraries designed for the rapid development of embedded software. GitHub 2017-01-23
Erika Enterprise Modified GPL MSP430 ARM AVR Erika Enterprise is the first open-source Free RTOS that has been certified OSEK/VDX compliant!. 2.7.0 Code 2016-06-15
scmRTOS MIT MSP430 AVR scmRTOS stands for Single-Chip Microcontroller Real-Time Operating System. v5.1.0 GitHub 2016-04-19
BitThunder GNU GPL version 2.0 ARM A Reliable Real-Time Operating System & Application Framework. stable-0.9.2 GitHub 2015-09-28
TI-RTOS Kernel Other TI-RTOS Kernel (formerly known as SYS/BIOS v3.00.00 2016-07-09
TNeo Other ARM TNeo is a well-formed and carefully tested preemptive real-time kernel for 16- and 32-bits MCUs. It is compact and fast. v1.08 GitHub 2017-02-25
LibreRTOS Apache License AVR LibreRTOS is a portable single-stack Real Time Operating System. All tasks share the same stack, allowing a large number or tasks to be created even on architectures with low RAM, such as ATmega328P (2kB). dev-master GitHub 2017-05-08
IntrOS GPL v3 ARM Free, simple and tiny cooperative operating system (OS) designed for deeply embedded applications. v2.8 GitHub 2017-04-02
embox Other MSP430 ARM MIPS PowerPC Embox is a configurable operating system kernel designed for resource constrained and embedded systems. v0.3.17 GitHub 2017-04-01
uKOS GPL v3 ARM uKOS is a multi-tasking OS suitable for small embedded µController systems. It is based on a preventive multitasking scheduler. 4.0.0 2017-04-26
seL4 Other ARM The world's first operating-system kernel with an end-to-end proof of implementation correctness and security enforcement is available as open source. 5.2.0 GitHub 2017-05-31
Trampoline GNU GPL version 2.0 ARM AVR PowerPC Trampoline is a static RTOS for small embedded systems. Its API is aligned with OSEK/VDX OS and AUTOSAR OS 4.2 standards. dev-master GitHub 2017-06-18

RTOSs not under active development ( Not updated for more than 2 years )

Name License Description Version Links Last updated
Femto OS GPL AVR Femto OS: RTOS for small MCU's like AVR. Code 2012-12-09
Protothreads BSD AVR 8051 Protothreads are extremely lightweight stackless threads designed for severely memory constrained systems. 2005-04-08
eCos GPL ARM MIPS PowerPC eCos is a free open source real-time operating system intended for embedded applications. The highly configurable nature of eCos allows the operating system to be customised to precise application requirements, delivering the best possible run-time perfor 2013-08-25
Freescale MQX Other ARM ColdFire The Freescale MQX Real-Time Operating System (RTOS) provides real-time performance within a small, configurable footprint. The RTOS is tightly integrated with the latest 32-bit MCUs and MPUs from Freescale and is provided with commonly used device drivers 4.2.0 2015-03-07
FunkOS Other MSP430 AVR FunkOS is an RTOS for 8-32 bit MCUs including AVR, MSP430, and Cortex M3. Both C and C++ kernels avaiable. Key features include preemption, periodic events, device drivers, and mutex/semaphores. Includes a variety of graphics and filesystem middleware. 2013-04-23
Fusion Embedded RTOS Other ARM PowerPC The Fusion Embedded RTOS (Real-Time Operating System) from Unicoi Systems is a Real-Time OS designed and optimized for networking and media-centric processors. 2015-03-08
MARK3 BSD AVR Mark3 is a sophisticated, modern RTOS and application development platform, targeted towards a growing list of today's most compelling embedded devices. Code 2015-03-08
Nut/OS GPL AVR ColdFire Nut/OS is an intentionally simple RTOS for the ATmega128, which provides a minimum of services to run Nut/Net, the TCP/IP stack. Code 2014-11-20
Prex BSD ARM x86 Prex is an open source, royalty-free, real-time operating system for embedded systems. It is designed and implemented for resource-constrained systems that require predictable timing behavior. The highly portable code of Prex is written in 100% ANSI C bas 0.9.0 Code 2009-10-01
TNKernel GPL MSP430 ColdFire TNKernel is a compact and very fast real-time kernel for the embedded 32/16/8 bits microprocessors. 2013-06-06
uSmartX BSD ARM AVR uSmartX is a non-preemptive, multitasking, priority based RTOS. 1.34 Code 2006-01-14
DuinOS Other AVR DuinOS is a small multithreading real time operating system (RTOS), based on the FreeRTOS kernel, for Arduino compatible boards. FreeRTOS_V7.4.0 GitHub 2013-04-02