Federated learning is a privacy-enhancing technology that we use to improve models on-device without sending your raw data to Google servers. Google uses federated learning to improve device activation such as “Hey Google” on Google Assistant-enabled devices.
When you ask, "Hey Google, what’s the weather tomorrow?" an on-device model detects that you said, “Hey Google,” and then sends your query to Google Assistant.
Also, on supported smart home devices with cameras, on-device models can store and use images to detect activation through gestures, gaze, and lip movement.
Your devices might activate unintentionally or trigger when you didn't say, “Hey Google.” In other cases, it might not trigger when you did say, “Hey Google.”
We now use federated learning to refine Assistant's activation technologies to reduce misactivations and misses.
Learn more about federated learning from Google AI’s online comic.
When “Improve how Assistant activates on your devices” is on and Google Assistant activates or nearly activates, it temporarily stores short bits of your voice recordings on your device. With federated learning, we use these recordings to learn how to adjust Assistant's speech and activation technologies.
When Google Assistant activates
When Google Assistant activates, including unintended activations, it may send your voice recording to Google servers so your Assistant can complete your request, like returning the weather forecast to your phone. These recordings are stored on Google servers if you have Web & App Activity turned on and include audio recordings.
When Google Assistant nearly activates
“Near activations” are cases when the “Hey Google” model detects audio, or something you said, that almost activated Google Assistant.
Your voice recordings from near activations aren’t sent to Google servers, but may be saved on your device if “Improve how Assistant activates on your devices” is on. Your device may not indicate anything when it stores these recordings and may store up to 20 recordings per day, along with:
- Data about how and when you interact with Assistant on your phone.
- How successful an interaction was.
- Phone configuration information.
How long recordings stay on your device
On-device recordings from “Hey Google" activations and near-activations stay on your device for up to 63 days unless you delete them before then. Learn how to delete your on-device recordings.
When “Improve how Assistant activates on your devices” is on and Google Assistant activates or nearly activates, it temporarily stores up to the first 20 words it hears. It also stores:
- How and when you interact with Assistant on your phone.
- Success of interactions.
- Phone configuration information.
We use this data to learn how to adjust Assistant's activation technologies without it ever leaving your device.
How long transcripts stay on your device
Transcripts and associated metadata used to help Assistant's activation technologies improve will stay on your device for up to 63 days unless you delete them. Learn how to delete your on-device transcripts.
When “Improve how Assistant activates on your devices” is on and Google Assistant activates, it temporarily stores images on your device. We use these images to learn how to adjust Assistant's activation technologies without the images ever leaving your device.
How long images stay on your device
Images used to help improve Assistant's activation technologies stay on your device for up to 63 days unless you delete them manually first. Learn how to delete your on-device images.
Google Assistant uses the voice recordings, transcripts, and images stored on your devices to refine Assistant's activation technologies. It learns how to adjust the model from the voice, transcript, and image data, and sends a summary of the model changes to Google’s servers. Google collects this information to provide better models for everyone.
Google Assistant performs federated learning computations on your device only when the device is idle, plugged in, and connected to Wi-Fi.
When Google Assistant nearly activates, the voice recording isn't sent to Google servers. Instead, it may be stored on your device.
When Google Assistant activates, it may send your voice recording to Google servers so your Assistant can complete your request. In addition, it may be stored on your device.
When your voice recording, transcript, or image is stored on your device, it's encrypted and only used to make improvements to Assistant's activation technologies. It's deleted when no longer needed, which is no more than 63 days.
Manage settings & your data
By default, the use of federated learning to improve Assistant's activation technologies is turned off.
Turn on federated learning for Assistant's activation technologies- On your Android phone or tablet, say "Hey Google, open Assistant settings."
- Under “All settings,” tap Help improve how Assistant activates. If you don't find the setting, first tap You.
- Turn on Improve how Assistant activates on your devices.
Turning on this setting will not affect how your data is collected, stored, or used under separate settings.
- On your Android phone or tablet, say "Hey Google, open Assistant settings."
- Under “All settings,” tap Help improve how Assistant activates. If you don't find the setting, first tap You.
- Turn off Improve how Assistant activates on your devices.
When you turn off federated learning for Assistant's activation technologies
- Google Assistant deletes the voice recordings, transcripts, and images that it stored on your device to improve activations of Google Assistant-enabled devices.
- “Hey Google” continues to work in the same way.
- Turning off this setting will not impact how your data is collected, stored, or used under separate settings. Assistant won’t delete the voice recordings stored on Google servers if you have Web & App Activity turned on and include audio recordings. Learn how to delete your voice recordings from Google servers.
In My Activity, you’ll find a list of your past activity on Google Assistant. If an activity includes a recording, it has an audio icon 
- Go to your Google Assistant Activity in My Activity.
- Choose the activity you want to delete:
- To delete a specific activity and recording: Next to the one you want to delete, select More
Delete.
- To delete all Google Assistant activity, not just activity with a recording: At the top right, select More
- To delete a specific activity and recording: Next to the one you want to delete, select More
Delete.- Go to your Activity controls.
- If Web & App Activity is turned on, uncheck the box next to "Include voice and audio activity."
- When Web & App Activity is turned off or “Include voice and audio activity” isn’t checked, Google Assistant doesn’t actively store your voice recordings on Google servers.
- On your Android phone or tablet, say "Hey Google, open Assistant settings" or go to Assistant settings.
- Under “All settings,” tap General.
- Turn off Google Assistant.