willow

Open source alternative to Google Home, Google Cloud Dialogflow, Amazon Alexa Custom Assistant, Microsoft Azure AI Speech and Picovoice

3.1K stars
Apache-2.0
Active this month
Last commit 22 days ago

Last verified Oct 20, 2026

Build a self-hosted voice assistant on $50 ESP32 hardware with Amazon Echo-competitive speed, local speech processing, and Apache 2.0 license.

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Read the full breakdownWho it is for, how it works, trade-offs and the FAQ

who it's for

Who willow is for#

Home automation users running Home Assistant or openHAB

Willow sends speech results as HTTP POST requests directly to Home Assistant or openHAB, with no cloud intermediary. If you have an existing self-hosted home automation setup, Willow adds voice control without introducing any cloud service to your stack. One device handles a room; install as many as you need.

Skip if:

If your home automation relies on commercial services like SmartThings or Alexa Routines that require vendor cloud APIs, Willow will not replace those integrations. It is designed for fully self-hosted automation stacks.

Privacy-focused households avoiding smart speaker data collection

Every voice command stays on your local network. On-device command recognition means nothing leaves the ESP32 chip for those commands. The Willow Inference Server path keeps inference on your own server. No commands are logged by Amazon or Google, and the source code is fully inspectable.

Skip if:

If you are comfortable with commercial smart speakers and have no concerns about voice data going to cloud providers, the setup complexity of Willow is not worth the trade-off compared to an Echo or Google Home device.

IoT and embedded developers building custom voice interfaces

Willow targets the ESP32-S3-BOX hardware family with the ESP-IDF framework under Apache 2.0, so you can fork the codebase and build custom voice interfaces for your own hardware projects. The Willow Inference Server adds STT, TTS, and LLM inference endpoints that work with any application, including WebRTC-based use cases.

Skip if:

If you need voice recognition across arbitrary hardware without writing firmware, a cloud API like Azure AI Speech or Google Cloud Dialogflow fits better than Willow's firmware-first approach.

Technically capable households wanting Echo-class performance without cloud

The project benchmarks note response times under 500ms from end of speech to completed action, far-field recognition from roughly 25 feet, and a tested failure rate below 1% across thousands of command cycles. For users who want smart speaker performance without cloud dependency, Willow provides a tested baseline competitive on those metrics.

Skip if:

If you want a device you can buy, plug in, and configure through a phone app with no technical setup required, Willow is not the right fit. It assumes willingness to flash firmware and configure REST endpoints.

the problem

The problem it solves#

Smart speakers from Amazon and Google are convenient, but every voice command you speak travels to cloud servers for processing. You have no visibility into what is retained, how long it is stored, or how it is used. For households with strict privacy requirements, this is a hard blocker.

The deeper problem for home automation users is dependency. Cloud-connected voice assistants require an active internet connection, vendor accounts, and ongoing platform support. When Amazon changes Alexa pricing or discontinues a skill integration, your setup breaks without recourse. Custom wake words, custom command vocabularies, and integration with self-hosted platforms like Home Assistant are locked behind proprietary APIs that require ongoing vendor relationships. Building voice automation on a commercial platform means renting the capability, not owning it.

how willow solves it

How it solves it#

Sub-500ms end-to-end response

Willow processes voice commands from end of speech to completed action in 500ms or less, matching or exceeding the response time of Amazon Echo and Google Home in equivalent scenarios. The speed comes from running speech recognition close to the hardware, with the Willow Inference Server handling inference tasks when on-device recognition is not used.

On-device command recognition for up to 400 commands

Configure up to 400 voice commands that run entirely on the ESP32 device with no network dependency. Voice Activity Detection handles endpoint detection automatically: it stops the listen cycle when you stop talking and triggers action without requiring manual confirmation.

Willow Inference Server for open-ended speech

For commands beyond the on-device vocabulary, the open source Willow Inference Server handles speech-to-text, text-to-speech, and LLM inference tasks. It supports WebRTC and runs on your own server infrastructure. Tovera provides a best-effort hosted instance so you can start without running your own server.

Home Assistant, openHAB, and REST API integration

Willow sends speech results as HTTP POST requests to any configured endpoint, including Home Assistant, openHAB, or any custom REST API. If your automation platform can accept an HTTP POST, it works with Willow. No vendor-specific protocol or cloud intermediary required.

Far-field audio with professional-grade processing

Willow is tested for wake word and speech recognition at roughly 25 feet in challenging acoustic environments. Audio processing includes automatic gain control, acoustic echo cancellation, noise suppression, and blind source separation, addressing the same acoustic problems commercial smart speakers solve but on hardware you own.

Dual wake word support with local detection

Willow ships with support for "Hi ESP" and "Alexa" as user-selectable wake words, with more planned. Wake word detection runs locally on the device, so the system does not need cloud connectivity to activate. Users can build and flash the firmware themselves to inspect or modify wake word behavior.

strengths · trade-offs

Strengths and trade-offs#

Strengths

Fully self-hosted with no cloud requiredWillow can operate entirely on your local network using on-device command recognition. No Amazon account, no Google account, no API keys, and no data leaving your home. For households with strict data handling requirements or a preference for local control, this is the differentiating capability compared to any cloud-connected smart speaker.
Apache 2.0 license with no usage restrictionsApache 2.0 means you can use, modify, and redistribute the firmware commercially with no licensing fees. Unlike proprietary smart speaker platforms where the vendor controls the skill SDK, the command vocabulary, and device certification, Willow gives you the source code and the freedom to change anything.
One-time $50 hardware cost with parts from standard retailersThe ESP32-S3-BOX-3 hardware costs approximately $50 USD fully assembled, plus a USB-C power supply. It is available from Amazon, AliExpress, Adafruit, The Pi Hut, Mouser, and other standard electronics retailers. No proprietary cables, no subscription, and no activation fee.
100mW power draw for always-on deploymentWillow draws approximately 100mW during operation, making it practical for always-on deployment without meaningful electricity cost. For households with many rooms, the low per-device power draw makes installing multiple units economically straightforward.

Trade-offs

-Requires ESP32-S3-BOX hardware and firmware flashingWillow is not a software download you run on existing hardware. You need to purchase an ESP32-S3-BOX-3 or compatible device (approximately $50), then build and flash the firmware yourself following the official documentation at heywillow.io. Non-technical users who expect plug-and-play setup will find the initial barrier significant compared to unboxing an Echo.
-Ecosystem is smaller than Alexa or Google HomeThe Willow project has 3,092 GitHub stars and 127 forks, compared to the mature third-party skill and integration ecosystems of Amazon Alexa and Google Home. If you depend on specific commercial skills, streaming service integrations, or shopping features that require vendor APIs, those are not available through Willow.
-Firmware customization requires embedded C knowledgeWillow's firmware is written in C using the ESP-IDF framework. Modifying the firmware, adding wake words beyond the defaults, or extending on-device vocabulary past 400 commands requires embedded C development skills. Users who want extensibility without writing C code need to rely on the Willow Inference Server path instead.

versus alternatives

willow vs alternatives#

Willow vs Amazon Alexa Custom Assistant

Amazon Alexa Custom Assistant is a cloud-hosted voice AI platform for building branded Alexa skills and custom voice experiences on AWS infrastructure. Willow is a self-hosted, open source firmware for ESP32 hardware that runs voice recognition locally without any Amazon cloud dependency.

Feature	Willow	Amazon Alexa Custom Assistant
License	Apache 2.0	Proprietary
Self-hosting	Full local deployment	Cloud-only (AWS required)
Voice data routing	On device or local server	Routed to AWS
Home automation	Native REST API to any endpoint	Via Alexa skill framework
Hardware cost	~$50 one-time	Varies by device

Willow is the better choice when your goal is keeping voice data on your own infrastructure and integrating directly with Home Assistant or openHAB without cloud intermediaries. The Apache 2.0 license lets you modify and redistribute the firmware; Amazon's Custom Assistant platform requires working within Alexa's skill framework and AWS infrastructure.

Amazon Alexa Custom Assistant is still the better choice when you need the broader Alexa skill ecosystem, Amazon Music, shopping integrations, or enterprise-grade cloud reliability. If your voice assistant use case depends on third-party Alexa skills that vendors have built specifically for Alexa and have not developed Willow integrations for, you will lose those capabilities.

Willow vs Google Cloud Dialogflow

Google Cloud Dialogflow is a natural language understanding platform hosted on Google Cloud that handles intent detection and entity extraction from speech or text, requiring an active Google Cloud account and metered API usage.

Feature	Willow	Google Cloud Dialogflow
License	Apache 2.0	Proprietary
Self-hosting	Full local deployment	Cloud-only (GCP required)
Pricing model	One-time hardware cost	Per-request API billing
On-device processing	Yes (up to 400 commands)	No
Home automation focus	Yes (HA, openHAB, REST)	General NLP platform

Willow addresses a different layer of the stack than Dialogflow. Willow handles wake word detection, voice activity detection, and speech capture on embedded hardware, then routes the result to your automation platform. Dialogflow is a cloud NLP service that processes text after speech-to-text has already run. Teams building voice automation for home use cases will find Willow's direct REST API integration simpler than constructing a Dialogflow agent to translate intents into Home Assistant calls.

Dialogflow is the better choice when you need sophisticated multi-turn conversation management, entity extraction across complex domains, or integration with Google Assistant for mobile and smart display devices. Willow is purpose-built for home automation command dispatch, not general conversational AI.

tech stack · detected from GitHub

What it's built on#

Languages: CPython

frequently asked

FAQ#

Does Willow work without an internet connection?

Yes, for on-device command recognition. Willow supports up to 400 voice commands configured entirely on the device with no network dependency for those commands. If you use the Willow Inference Server for open-ended speech recognition, that server can also run on your local network without internet access. Cloud connectivity is optional, not required.

What hardware does Willow require?

Willow targets the ESP32-S3-BOX hardware family from Espressif, primarily the ESP32-S3-BOX-3. This device costs approximately $50 USD fully assembled and is available from Amazon, AliExpress, Adafruit, The Pi Hut, and Mouser. You also need a USB-C power supply. No other hardware is required for basic operation.

How does Willow connect to Home Assistant?

Willow sends speech results as standard HTTP POST requests to any configured REST API endpoint. Point it at your Home Assistant instance URL and it delivers voice command results directly. No cloud service, no Alexa skill, and no Google integration is required. openHAB works the same way through the same REST API path.

Is Willow free to use?

Yes. The firmware is Apache 2.0 licensed, meaning free to use, modify, and redistribute including for commercial purposes. Your only cost is the approximately $50 hardware. Tovera provides a best-effort hosted Willow Inference Server at no charge, or you can self-host one on your own server at no additional software cost.

How fast is Willow compared to Alexa or Google Home?

Willow targets under 500ms from the end of your speech to a completed action. According to the project's own benchmarks, this matches or exceeds Alexa and Google Home response times in equivalent test scenarios. The speed comes from minimizing cloud round-trips: inference runs on the device itself or on a local server rather than traveling to a remote data center.

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Willow vs Amazon Alexa Custom Assistant

Feature	Willow	Amazon Alexa Custom Assistant
License	Apache 2.0	Proprietary
Self-hosting	Full local deployment	Cloud-only (AWS required)
Voice data routing	On device or local server	Routed to AWS
Home automation	Native REST API to any endpoint	Via Alexa skill framework
Hardware cost	~$50 one-time	Varies by device

Willow vs Google Cloud Dialogflow

Feature	Willow	Google Cloud Dialogflow
License	Apache 2.0	Proprietary
Self-hosting	Full local deployment	Cloud-only (GCP required)
Pricing model	One-time hardware cost	Per-request API billing
On-device processing	Yes (up to 400 commands)	No
Home automation focus	Yes (HA, openHAB, REST)	General NLP platform

Who willow is for#

Home automation users running Home Assistant or openHAB

Skip if:

Privacy-focused households avoiding smart speaker data collection

Skip if:

IoT and embedded developers building custom voice interfaces

Skip if:

Technically capable households wanting Echo-class performance without cloud

Skip if:

The problem it solves#

How it solves it#

Sub-500ms end-to-end response

On-device command recognition for up to 400 commands

Willow Inference Server for open-ended speech

Home Assistant, openHAB, and REST API integration

Far-field audio with professional-grade processing

Dual wake word support with local detection

Strengths and trade-offs#

Strengths

Trade-offs

willow vs alternatives#

Willow vs Amazon Alexa Custom Assistant

Willow vs Google Cloud Dialogflow

What it's built on#

FAQ#

Similar open-source tools#

Open source tools in these categories#

AI & Machine Learning

Cloud & Hosting

Web Development

Find open source alternatives to paid software

Who willow is for#

Home automation users running Home Assistant or openHAB

Skip if:

Privacy-focused households avoiding smart speaker data collection

Skip if:

IoT and embedded developers building custom voice interfaces

Skip if:

Technically capable households wanting Echo-class performance without cloud

Skip if:

The problem it solves#

How it solves it#

Sub-500ms end-to-end response

On-device command recognition for up to 400 commands

Willow Inference Server for open-ended speech

Home Assistant, openHAB, and REST API integration

Far-field audio with professional-grade processing

Dual wake word support with local detection

Strengths and trade-offs#

Strengths

Trade-offs

willow vs alternatives#

Willow vs Amazon Alexa Custom Assistant

Willow vs Google Cloud Dialogflow

What it's built on#

FAQ#

Similar open-source tools#

Open source tools in these categories#

AI & Machine Learning

Cloud & Hosting

Web Development

Find open source alternatives to paid software