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Privacy Policy

Last updated: September 2026

Overview

Circadianly is built with privacy as a core principle. The extension's core features operate entirely on your device. A few capabilities involve data outside the core local rhythm model: an optional Google Calendar integration that reads your calendar events and processes them on-device with Chrome's built-in AI, an optional Yahht account, and usage analytics. This policy explains exactly what is collected, by whom, and why.

What we collect

Core extension

Your wake-up time and preferences are stored locally using the Chrome Storage API and never leave your device.

Google Calendar integration (optional)

If you connect Google Calendar, Circadianly reads your calendar events — including event titles, times, descriptions, and attendee information — and processes them entirely on your device using Chrome's built-in AI (Gemini Nano) to generate personalised phase advice. No calendar data is transmitted to external AI servers. You can revoke access at any time from the extension settings or from your Google Account permissions page.

Yahht account (optional)

Circadianly is part of the Yahht family of extensions and works fully without an account. If you choose Sign in, you sign in on account.yahht.com with Google. Yahht ID receives your Google account ID, email address and name to identify your account; it never receives your password. The website then passes your Yahht account ID to the extension. If you have already signed in to Yahht in this browser, the extension reconnects to your account automatically in the background, without showing any window. How Yahht ID handles account data is described in the Yahht ID Privacy Policy.

Usage analytics

Circadianly uses PostHog to collect usage data — which features you interact with and how you use the extension, together with the extension version, browser and operating system. Each installation is assigned a random identifier. It is not linked to your name, email address, or Google account unless you sign in to a Yahht account: after sign-in, usage data is associated with your Yahht account ID. When you remove the extension, Chrome opens our uninstall page, which records the removal under the same random identifier. We use this data solely to understand how the extension is used and to improve it. Opt-out controls are planned for a future version.

Local storage

The extension stores the following data locally on your device:

  • Your wake-up time (used to compute the five circadian phase windows)
  • Extension preferences and settings
  • A boolean flag indicating whether you have connected Google Calendar (only the connection state, not the token itself)
  • The random installation identifier used for analytics
  • If you sign in: your Yahht account ID and, if you have a Yahht subscription, signed access tokens that confirm it

The installation identifier and account data are kept in Chrome's synced extension storage, so they follow your Chrome profile across your devices when Chrome Sync is on. None of this data is transmitted anywhere except as described above.

Permissions

Circadianly requests the following browser permissions:

  • storage — saves your local preferences and wake time between sessions
  • identity — authenticates with Google when you enable the Calendar integration, and reconnects your Yahht account in the background if you have signed in before
  • https://www.googleapis.com/auth/calendar.readonly — grants read-only access to your Google Calendar events, requested only when you enable the Calendar integration

Third-party services

  • Google Calendar API — provides read-only access to your calendar events when the integration is enabled. Calendar data is processed on-device and is not shared with Google for AI purposes.
  • Chrome Built-in AI (Gemini Nano) — an on-device AI model built into Chrome that processes your calendar events locally to generate phase advice. No data leaves your device during inference.
  • Yahht ID (account.yahht.com) — the Yahht account service, used only if you sign in.
  • PostHog — collects usage analytics identified by a random installation ID, or by your Yahht account ID after you sign in.

Google API Services — Limited Use

Circadianly's use and transfer to any other app of information received from Google APIs will adhere to the Google API Services User Data Policy, including the Limited Use requirements.

Specifically, Circadianly:

  • Only reads calendar data to provide the personalised phase advice feature directly requested by you.
  • Does not transfer Google user data to third parties except as necessary to provide the extension's features.
  • Does not use Google user data for advertising or to train AI/ML models outside of your device.
  • Does not allow humans to read Google user data unless you have given explicit permission, it is necessary for security purposes, or it is required by law.

Data security

We apply the following protections to sensitive data handled by Circadianly:

  • OAuth token — never stored by the extension itself. Chrome's Identity API (chrome.identity) manages the token internally in Chrome's own secure token cache. The extension only calls chrome.identity.getAuthToken() to obtain a short-lived token for the duration of an API request.
  • Calendar event data — read from the Google Calendar API at the moment you request phase advice, processed in-memory on your device by Gemini Nano, and immediately discarded. No calendar content is ever written to persistent storage.
  • Data minimisation — the extension requests only the calendar.readonly scope and reads only the events needed to compute advice for the current time window.
  • No external transmission — calendar data, event titles, descriptions, and attendee information are never sent to Yahht servers or any third-party AI service.
  • No data sales — we do not sell, rent, or share your personal data or Google user data with any third party for commercial purposes.

Your choices

  • Google Calendar: you can disconnect at any time from the extension settings, which removes the stored OAuth token and stops any calendar data from being sent.
  • Yahht account: signing in is optional. You can manage your account at account.yahht.com. To delete it and its personal data, write to mail@yahht.com.
  • Analytics: opt-out controls are planned for a future version of the extension.

Children's privacy

Circadianly is not directed at children under 13. The Google Calendar integration accesses personal calendar data and should not be used by children under 13.

Changes to this policy

If we make material changes to this policy, we will update the date at the top of this page and release a new version of the extension.

Contact

Questions? Reach us at mail@yahht.com.