Introducing Zephyr

The Zephyr OS is based on a small-footprint kernel designed for use on resource-constrained systems: from simple embedded environmental sensors and LED wearables to sophisticated smart watches and IoT wireless gateways.

The Zephyr kernel supports multiple architectures, including ARM Cortex-M, Intel x86, ARC, NIOS II, Tensilica Xtensa, and RISC-V. The full list of supported boards can be found here.


Zephyr is permissively licensed using the Apache 2.0 license (as found in the LICENSE file in the project’s GitHub repo). There are some imported or reused components of the Zephyr project that use other licensing, as described in Licensing of Zephyr Project components.

Distinguishing Features

The Zephyr kernel offers a number of features that distinguish it from other small-footprint OSes:

Single address-space
Combines application-specific code with a custom kernel to create a monolithic image that gets loaded and executed on a system’s hardware. Both the application code and kernel code execute in a single shared address space.
Highly configurable / Modular for flexibility
Allows an application to incorporate only the capabilities it needs as it needs them, and to specify their quantity and size.
Cross Architecture
Supports a wide variety of supported boards with different CPU architectures and developer tools. Contributions have added support for an increasing number of SoCs, platforms, and drivers.
Compile-time resource definition
Allows system resources to be defined at compile-time, which reduces code size and increases performance for resource-limited systems.
Minimal and Configurable error checking
Provides minimal runtime error checking to reduce code size and increase performance. An optional error-checking infrastructure is provided to assist in debugging during application development.
Memory Protection
Implements configurable architecture-specific stack-overflow protection, kernel object and device driver permission tracking, and thread isolation with thread-level memory protection on x86, ARC, and ARM architectures, userspace, and memory domains.
Native Networking Stack supporting multiple protocols
Networking support is fully featured and optimized, including LwM2M and BSD sockets compatible support. Bluetooth Low Energy 5.0 support includes BLE Mesh and a Bluetooth qualification-ready BLE controller. OpenThread support (on Nordic chipsets) is also provided - a mesh network designed to securely and reliably connect hundreds of products around the home.
Native Linux, macOS, and Windows Development
A command-line CMake build environment runs on popular developer OS systems. A native POSIX port, lets you build and run Zephyr as a native application on Linux and other OSes, aiding development and testing.
Extensive suite of services

Zephyr offers a number of familiar services for development:

  • Multi-threading Services for cooperative, priority-based, non-preemptive, and preemptive threads with optional round robin time-slicing. Includes pthreads compatible API support.
  • Interrupt Services for compile-time registration of interrupt handlers.
  • Memory Allocation Services for dynamic allocation and freeing of fixed-size or variable-size memory blocks.
  • Inter-thread Synchronization Services for binary semaphores, counting semaphores, and mutex semaphores.
  • Inter-thread Data Passing Services for basic message queues, enhanced message queues, and byte streams.
  • Power Management Services such as tickless idle and an advanced idling infrastructure.
  • File system with Newtron Flash Filesystem (NFFS) and FATFS support, FCB (Flash Circular Buffer) for memory constrained applications, and file system enhancements for logging and configuration.
  • ZTest infrastructure and a coverage test suite for continuous integration testing and verification as features are added and updated.

Community Support

The Zephyr Project Developer Community includes developers from member organizations and the general community all joining in the development of software within the Zephyr Project. Members contribute and discuss ideas, submit bugs and bug fixes, and provide training. They also help those in need through the community’s forums such as mailing lists and IRC channels. Anyone can join the developer community and the community is always willing to help its members and the User Community to get the most out of the Zephyr Project.

Welcome to the Zephyr community!


Here’s a quick summary of resources to find your way around the Zephyr Project support systems:

  • Zephyr Project Website: The website is the central source of information about the Zephyr Project. On this site, you’ll find background and current information about the project as well as all the relevant links to project material. For a quick start, refer to the Zephyr Introduction and Getting Started Guide.

  • Releases: Source code for Zephyr kernel releases are available at On this page, you’ll find release information, and links to download or clone source code from our GitHub repository. You’ll also find links for the Zephyr SDK, a moderated collection of tools and libraries used to develop your applications.

  • Source Code in GitHub: Zephyr Project source code is maintained on a public GitHub repository at You’ll find information about getting access to the repository and how to contribute to the project in this Contribution Guide document.

  • Samples Code: In addition to the kernel source code, there are also many documented Sample and Demo Code Examples that can help show you how to use Zephyr services and subsystems.

  • Documentation: Extensive Project technical documentation is developed along with the Zephyr kernel itself, and can be found at Additional documentation is maintained in the Zephyr GitHub wiki.

  • Cross-reference: Source code cross-reference for the Zephyr kernel and samples code is available at

  • Issue Reporting and Tracking: Requirements and Issue tracking is done in the Github issues system: You can browse through the reported issues and submit issues of your own.

  • Security-related Issue Reporting and Tracking: For security-related inquiries or reporting suspected security-related bugs in the Zephyr OS, please send email to We will assess and fix flaws according to our security policy outlined in the Zephyr Project Security Overview.

    Security related issue tracking is done in JIRA. The location of this JIRA is

  • Mailing List: The Zephyr Development mailing list is perhaps the most convenient way to track developer discussions and to ask your own support questions to the Zephyr project community. There are also specific Zephyr mailing list subgroups for announcements, builds, marketing, and Technical Steering Committee notes, for example. You can read through the message archives to follow past posts and discussions, a good thing to do to discover more about the Zephyr project.

  • IRC Chatting: You can chat online with the Zephyr project developer community and other users in our IRC channel #zephyrproject on the IRC server. You can use the web client or use a client-side application such as pidgin.

Fundamental Terms and Concepts

See Glossary of Terms