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.

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

Tock is an embedded operating system designed for running multiple concurrent, mutually distrustful applications on Cortex-M based embedded platforms. The kernel and device drivers are written in Rust.

QuarkTS is a simple non-Preemtive Real-Time OS with a quasi-static scheduler for embedded multi-tasking applications.

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.

Phoenix-RTOS is an open-source, microkernel-based, realtime operating system for resource constrained devices.

TencentOS tiny is a real-time operating system developed by Tencent for the Internet of Things. It features low power consumption, low resource consumption, modularity, security and reliability, and can effectively improve the development efficiency of IoT terminal products.

StratifyOS is a powerful embedded RTOS for the ARM Cortex M microcontrollers.

This advanced real-time operating system (RTOS) is designed specifically for deeply embedded applications. Among the multiple benefits it provides are advanced scheduling facilities, message passing, interrupt management, and messaging services. Azure RTOS ThreadX has many advanced features, including picokernel architecture, preemption threshold, event chaining, and a rich set of system services.

FreeRTOS is a market leading RTOS from Amazon Web Services that supports more than 35 architectures. It is distributed under the MIT license.

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.

Contiki-NG is an operating system for resource-constrained devices in the Internet of Things. Contiki-NG contains an RFC-compliant, low-power IPv6 communication stack, enabling Internet connectivity.

Embox is a configurable operating system kernel designed for resource constrained and embedded systems.

The worlds first operating-system kernel with an end-to-end proof of implementation correctness and security enforcement is available as open source.

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.

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

Trampoline is a static RTOS for small embedded systems. Its API is aligned with OSEK/VDX OS and AUTOSAR OS 4.2 standards.

μC/OS-II is a portable, ROMable, scalable, preemptive, real-time deterministic multitasking kernel for microprocessors, microcontrollers and DSPs.

µC/OS-III is a highly portable, ROMable, scalable, preemptive, real-time, deterministic, multitasking kernel for microprocessors, microcontrollers and DSPs.

Drone is an Embedded Operating System for writing real-time applications in Rust.

TinyOS is an open source, BSD-licensed operating system designed for low-power wireless devices, such as those used in sensor networks, ubiquitous computing, personal area networks, smart buildings, and smart meters.

AliOS Things is designed for low power, resource constrained MCU, connectivity SoC, greatly suitable for IoT devices. AliOS Things is not just a RTOS, it contains full stack of software components and tools for building IoT devices.

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).

Mongoose OS - an open source Operating System for Internet of Things. Supported microcontrollers: ESP32, ESP8266, CC3220, CC3200, STM32F4. Amazon AWS IoT Google IoT Core integrated. Code in C or JavaScript.

scmRTOS is tiny Real-Time Preemptive Operating System intended for use with Single-Chip Microcontrollers. scmRTOS is capable to run on tiny uCs with as small amount of RAM as 512 bytes. The RTOS is written on C++ and supports various platforms.

Nut/OS is an intentionally simple RTOS for the ATmega128, which provides a minimum of services to run Nut/Net, the TCP/IP stack.

ChibiOS is a complete development environment for embedded applications including RTOS, an HAL, peripheral drivers, support files and a development environment.

DuinOS is a small multithreading real time operating system (RTOS), based on the FreeRTOS kernel, for Arduino compatible boards.

Free, extremely simple and amazingly tiny real-time operating system (RTOS) designed for deeply embedded applications. Target: ARM Cortex-M, STM8. It was inspired by the concept of a state machine.

Free, simple and tiny cooperative operating system (OS) designed for deeply embedded applications.

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.

TizenRT is a lightweight RTOS-based platform to support low-end IoT devices

Erika Enterprise is the first open-source Free RTOS that has been certified OSEK/VDX compliant!.

Huawei LiteOS is a lightweight open-source IoT OS and a smart hardware development platform. It simplifies IoT device development and device connectivity, makes services smarter, delivers superb user experience, and provides better data protection. Huawei LiteOS is designed for smart homes, wearables, IoV, and intelligent manufacturing applications.

Frosted is an acronym that means Free Operating Systems for Tiny Embedded Devices. The goal of this project is to provide a Free (as in Freedom) kernel for embedded systems, which exposes a POSIX-compliant system call API.

distortos is an object-oriented C++ RTOS for microcontrollers.

The hyperC OS is a real time-operating system (RTOS) designed for various IoT applications. All the designs are aimed at the optimization of ARM Cortex CPUs.

The eChronos RTOS is a real-time operating system (RTOS) originally developed by NICTA and Breakaway Consulting Pty. Ltd. It is intended for tightly resource-constrained devices without memory protection.

Contiki is an open source operating system for the Internet of Things. Contiki connects tiny low-cost, low-power microcontrollers to the Internet.

BeRTOS is a real time open source operating system supplied with drivers and libraries designed for the rapid development of embedded software.

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.

cocoOS is a free, open source, cooperative task scheduler, based on coroutines targeted for embedded microcontrollers like AVR, MSP430 and STM32.

BRTOS is a lightweight preemptive real time operating system designed for low end microcontrollers.

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.

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

Atomthreads is a free, lightweight, portable, real-time scheduler for embedded systems.

uKOS is a multi-tasking OS suitable for small embedded µController systems. It is based on a preventive multitasking scheduler.

MOE is an event-driven scheduler system for 8/16/32-bit MCUs. MOE means Minds Of Embedded system.

The TOPPERS/ATK (Automotive Kernel) is a real-time operating system for automotive system control publicly released by the TOPPERS project.

TNeo is a well-formed and carefully tested preemptive real-time kernel for 16- and 32-bits MCUs. It is compact and fast.

MaRTE OS is a Hard Real-Time Operating System for embedded applications that follows the Minimal Real-Time POSIX.13 subset.

A Reliable Real-Time Operating System Application Framework.

TI-RTOS Kernel (formerly known as SYS/BIOS

Mark3 is a sophisticated, modern RTOS and application development platform, targeted towards a growing list of todays most compelling embedded devices.

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.

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

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

TNKernel is a compact and very fast real-time kernel for the embedded 32/16/8 bits microprocessors.

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.

Femto OS: RTOS for small MCUs like AVR.

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

uSmartX is a non-preemptive, multitasking, priority based RTOS.

Protothreads are extremely lightweight stackless threads designed for severely memory constrained systems.