Zephyr Project Documentation

Welcome to the Zephyr Project’s documentation version 1.4.0!

Documentation for the development branch of Zephyr can be found at https://www.zephyrproject.org/doc/

Introduction to the Zephyr Project

The Zephyr Kernel is 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.

It is designed to be supported by multiple architectures, including ARM Cortex-M, Intel x86, and ARC. The full list of supported platforms can be found here.


The Zephyr project associated with the kernel makes it available to users and developers under the Apache License, version 2.0.

Distinguishing Features

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

  1. Single address-space OS. 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.
  2. Highly configurable. Allows an application to incorporate only the capabilities it needs as it needs them, and to specify their quantity and size.
  3. Resources defined at compile-time. Requires all system resources be defined at compilation time, which reduces code size and increases performance.
  4. Minimal error checking. Provides minimal run-time error checking to reduce code size and increase performance. An optional error-checking infrastructure is provided to assist in debugging during application development.
  5. Extensive suite of services Offers a number of familiar services for development:
    • Multi-threading Services for both priority-based, non-preemptive fibers and priority-based, preemptive tasks with optional round robin time-slicing.
    • Interrupt Services for both compile-time and run-time registration of interrupt handlers.
    • 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.
    • Memory Allocation Services for dynamic allocation and freeing of fixed-size or variable-size memory blocks.
    • Power Management Services such as tickless idle and an advanced idling infrastructure.

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