Real-time operating systems (RTOS) are important for embedded devices because they allow time-sensitive operations to be performed both reliably and on time. In all sorts of scenarios—whether it is controlling an infusion pump in healthcare, managing safety systems in vehicles, or running smart home devices—an RTOS enables repeatability and fast reaction times. In this article, we identify the top 7 real-time operating systems (RTOSs) you would use in embedded devices in 2025, the properties and applications of them, and how to choose which RTOS would be best for your project.
Key Takeaways
RTOS, also called Real-time Operating Systems, enables tasks in an embedded system to be executed in a timely and predictable manner.
Examples of popular RTOS include FreeRTOS, Zephyr, VxWorks, QNX, SafeRTOS, Integrity, and embOS, to name just a few.
Considerations in choosing an RTOS include things like latency, memory footprint, certification for safety systems, and license type.
RTOS are used in numerous sectors, particularly and everywhere an embedded system is used, including automotive, industrial, Internet of Things (IoT), medical, aerospace, etc.
Some of the new trends look at security, multi-core and cloud support features.
What is a Real-Time Operating System?
Understanding RTOS
A Real-Time Operating System (RTOS) is an operational system that is more specialized than a standard operational system, designed to manage the hardware resources and run multiple tasks on embedded systems where time is critical. An RTOS is different from a general-purpose operating system (such as Windows or Linux) in that a standard OS does not have to guarantee that a high-priority task will complete in a certain amount of time. If it does not, the system may fail—especially if it is a safety-critical system.
For example, in an ABS system (anti-lock braking system), an accident may be avoided through early detection and response of wheel slip. This is accomplished by the responsiveness of an RTOS, which is due to prioritized tasks and low-latency.
Why RTOS are Essential in Embedded Systems
Embedded devices typically work under strict constraints of power, memory, and CPU. However, they must respond instantly when an event occurs. Ideally, RTOS offer:
Deterministic task scheduling: Tasks execute as scheduled.
Low interrupt latency: Hardware signals are responded to immediately.
Priority multitasking: Tasks are preempted for higher priority tasks.
When these factors are addressed properly, RTOS minimizes timing delays and improves safety and reliability of embedded systems.
How to Choose the Right RTOS for Embedded Devices
When selecting an RTOS, there are many competing considerations:
Performance and latency: The OS needs to meet real-time deadlines as well as minimize jitter (variation in response time).
Memory footprint: Embedded systems often have limited memory (either flash or RAM). The RTOS should use as little of either as comfortably possible.
Safety certifications: The RTOS may need to comply with a safety standard if you’re working in a safety-critical application (e.g., IEC 61508, ISO 26262).
Hardware compatibility: The RTOS must support the specific microcontroller or processor in the device.
Licensing: Open-source RTOS (e.g., FreeRTOS, Zephyr) are free but offer limited commercial support. Proprietary RTOS (e.g., VxWorks, QNX) offer premium features with commercial support.
Community and vendor support: Tools, documentation, forums, and official support can speed up development.
New RTOS trends focus on security, multi-core support, and cloud integration—especially relevant in IoT applications.
Top 7 Real-Time Operating Systems in Embedded Devices
1. FreeRTOS
FreeRTOS is the most popular RTOS—open-source or not—around the globe. It provides lightweight preemptive scheduling ideal for small microcontrollers typically found in consumer electronics and IoT devices. FreeRTOS is easily portable and has a very active community.
FreeRTOS is now provided by Amazon Web Services (AWS), with added features for secure cloud connectivity.
2. Zephyr OS
Zephyr OS is a modular, open-source RTOS designed for resource-constrained embedded and IoT applications. It supports many architectures including ARM Cortex-M and RISC-V, and features a full networking stack.
Zephyr is well-suited for industrial and smart home devices due to its focus on security and evolving safety certifications.
3. VxWorks
VxWorks is a commercial RTOS by Wind River, built for aerospace, defense, automotive, and similar industries. It offers hard real-time guarantees, deterministic scheduling, and low-latency operations.
VxWorks has powered NASA Mars rovers and numerous avionics systems.
4. Integrity
Integrity RTOS is designed for safety and security in embedded systems. It’s used in medical, aerospace, and defense applications that demand strict safety and fault tolerance.
Integrity offers strong memory isolation, fault containment, and industry-required safety certifications.
5. SafeRTOS
SafeRTOS is based on FreeRTOS and is built for applications needing compliance with functional safety standards like IEC 61508 SIL 3 and ISO 26262 ASIL D. It’s used in automotive, medical, and regulated markets.
SafeRTOS brings the simplicity of FreeRTOS with added certification support.
6. QNX
QNX is a Unix-like microkernel RTOS known for fault tolerance and security. It’s heavily used in automotive infotainment, industrial automation, and healthcare devices.
Its modular architecture and multicore support make it suitable for real-time and high-throughput applications.
7. embOS
embOS is a commercial RTOS developed for minimal latency and high efficiency on low-resource devices. It’s widely used in safety-critical automotive and industrial systems.
embOS is certified to standards like IEC 61508 and ISO 26262, and supports deterministic behavior with middleware flexibility.
Conclusion
Selecting the appropriate real-time operating system (RTOS) is determined by factors such as performance, memory requirements, safety and security assurance (safety is a huge area of development in the RTOS space) and hardware support. FreeRTOS, Zephyr, VxWorks, Integrity, SafeRTOS, QNX and embOS are all leading examples of RTOS that support various styles of embedded applications.
However, with modern trends in areas such as security, cloud-based systems and modern hardware support, maintaining ongoing employee development training is essential to ensure that teams remain up to date. An appropriate RTOS enables developers to build dependable real-time systems for an increasingly connected world
FAQ
Which RTOS is best for IoT embedded devices?
FreeRTOS and Zephyr OS are the most popular choices for IoT projects. FreeRTOS offers lightweight simplicity and cloud integration, while Zephyr provides advanced security and modular support for varied hardware.
How does RTOS ensure real-time performance?
An RTOS will utilize deterministic scheduling algorithms for tasks, and tasks will be preempted in accordance with priority levels (i.e. preempt less important tasks to allow high priority tasks to run with minimal latency.) For an RTOS it is also important to have minimum interrupt latency, and provide mechanisms for careful task synchronization.
