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| Zephyr | |
|---|---|
 Zephyr Project logo | |
| Developer | Linux Foundation, Wind River Systems |
| Written in | C |
| OS family | Real-time operating systems |
| Working state | Current |
| Source model | Open source |
| Initial release | 26 July 2016[1] |
| Latest release | 4.2.0 / 19 July 2025[2][3] |
| Repository | |
| Marketing target | Internet of things, embedded systems |
| Available in | English |
| Supported platforms | ARM (Cortex-M, Cortex-R, Cortex-A), ARC, MIPS, Nios II, RISC-V, Xtensa, SPARC, x86, x86-64 |
| Kernel type | Microkernel (pre-v1.6)[4][5][6] Monolithic (v1.6+)[5][6] |
| License | Apache 2.0 |
| Preceded by | Wind River Rocket |
| Official website | www |
Zephyr (/ˈzɛf ər/) is a small real-time operating system (RTOS)[7] for connected, resource-constrained and embedded devices (with an emphasis on microcontrollers) supporting multiple architectures and released under the Apache License 2.0. Zephyr includes a kernel, and all components and libraries, device drivers, protocol stacks, file systems, and firmware updates, needed to develop full application software.[8]
It is named after Zephyrus, the ancient Greek god of the west wind.[9]
Zephyr originated from Virtuoso RTOS for digital signal processors (DSPs).[10][11] In 2001, Wind River Systems acquired Belgian software company Eonic Systems, the developer of Virtuoso. In November 2015, Wind River Systems renamed the operating system to Rocket, made it open-source and royalty-free.[11] Compared to Wind River's other RTOS, VxWorks, Rocket had much smaller memory needs, especially suitable for sensors and single-function embedded devices. Rocket could fit into as little as 4 KB of memory, while VxWorks needed 200 KB or more.[11]
In February 2016, Rocket became a hosted collaborative project of the Linux Foundation under the name Zephyr.[10][12][1] Wind River Systems contributed the Rocket kernel to Zephyr, but still provided Rocket to its clients, charging them for the cloud services.[13][11] As a result, Rocket became "essentially the commercial version of Zephyr".[13]
Since then, early members and supporters of Zephyr include Intel, NXP Semiconductors, Synopsys, Linaro,[14] Texas Instruments, Nordic Semiconductor, Oticon, and Bose.[15]
As of January 2025[update], Zephyr had the largest number of contributors and commits compared to other RTOSes (including Mbed, RT-Thread, NuttX, and RIOT).[16]
Zephyr intends to provide all components needed to develop resource-constrained and embedded or microcontroller-based applications. This includes:[8]
Zephyr uses Kconfig and devicetree as its configuration systems, inherited from the Linux kernel, but implemented in Python programming language for portability to non-Unix operating systems.[17] The RTOS build system is based on CMake, which allows Zephyr applications to be built on Linux, macOS, and Microsoft Windows.[18]
Zephyr has a general-purpose tool called West for managing repositories, downloading programs to hardware, etc.
Early Zephyr kernels used a dual nanokernel plus microkernel design.[4][5][6] In December 2016, with Zephyr 1.6, this changed to a monolithic kernel.[5][6]
The kernel offers several features that distinguish it from other small OSes:[8]
A group is dedicated to maintaining and improving the security.[19] Also, being owned and supported by a community means the world's open source developers are vetting the code, which significantly increases security.[12]
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