1. Overview
LayerGlyph ("we", "us") is a local-first personal knowledge management tool that helps you collect and organize your Kindle highlights and web notes. Your highlights, notes, book reviews, and reading status are stored on your own device — not on our servers — by default. This policy explains what data exists, where it lives, and the (currently limited) cases where anything leaves your device.
2. Data We Handle
- Kindle highlights, notes, book reviews, reading status — Fetched from your Amazon Kindle notebook page and stored locally in your browser (IndexedDB via Dexie, through the LayerGlyph Chrome extension). This is the primary and default storage location; nothing here is uploaded to our servers unless you take a separate, explicit action. We never receive your Amazon credentials.
- Web highlights and bookmarks — Text and URLs you save using the LayerGlyph browser extension, also stored locally in your browser's IndexedDB.
- Tags — Tags you manually add to organize your content, stored locally alongside the content they tag.
- Account information (optional) — If you choose to sign in with Google (currently only needed for the optional Notion export integration), we receive your email address and Google account ID via Supabase Auth. Signing in is not required to use LayerGlyph's core features.
3. How We Use Your Data
- To display, search, and organize your highlights, notes, and reviews — entirely within your browser, reading from local IndexedDB storage.
- If you explicitly enable the optional Notion export feature, the relevant content is sent to Notion's API to create pages in your own Notion workspace. This only happens when you take that specific action.
- We do not sell your data to third parties.
- We do not use your highlight, note, or review content to train AI models.
- We do not share your reading data with advertisers.
- We do not send your highlight text, memo text, or book review body text off your device without your explicit, separate consent for a specific feature (like Notion export).
4. Data Storage
LayerGlyph is local-first: your highlights, notes, book reviews, and reading status are stored in your browser's IndexedDB (via Dexie, through the Chrome extension), on your own device. This is the primary storage location, and this content is not uploaded to any server by default.
An optional Cloud Backup/Sync feature is planned but is not enabled in the current release — it is gated behind an internal backupSyncEnabled flag that defaults to off, and there is no UI in the app today to turn it on. If and when it ships, it will require your explicit, separate opt-in and will remain off by default. This is a distinct setting from the anonymous product-improvement data described in Section 5 below — the two are never combined or treated as the same toggle.
Supabase(hosted Postgres, on AWS) is used only for optional account authentication (Google sign-in for the Notion integration) — it is not where your highlight, note, or review content lives, and we do not rely on database row-level security alone to protect your content, because that content simply isn't stored there in the first place.
5. Anonymous Product-Improvement Data (Discovery)
LayerGlyph plans a future feature that recommends books based on anonymous usage signals (not highlight/note/review text). This is controlled by a separate discoveryDataSharingEnabled setting, off by default. As of this release, the event-sending code path has not shipped yet — no such data is currently transmitted, whether or not any related setting is toggled. Even once this feature ships, it will never include your highlight text, memo text, or book review body text.
6. Analytics (PostHog)
We use PostHog for limited, anonymous product analytics. Recommendation-click events are only recorded when an explicit environment flag (NEXT_PUBLIC_POSTHOG_RECOMMENDATION_EVENTS_ENABLED) is set to true on our servers — this flag is off by default, meaning this specific analytics event does not fire in the current release regardless of your settings.
7. Other Network Requests
Loading the app may involve a small number of other read-only network requests that don't include your personal content: static assets and fonts from our hosting provider, book cover images from the Catalog CDN or Amazon, and — if you click through to buy a book — an outbound link to Amazon's site. None of these transmit your highlights, notes, reviews, or bookmarks.
8. Chrome Extension Permissions
The LayerGlyph browser extension requests the following permissions:
- storage — To save your local highlight/note/review data, authentication token (if signed in), and sync status.
- tabs — To open the Kindle notebook page for syncing and to detect the active tab URL for bookmarking.
- scripting — To inject the highlight selection UI on web pages.
- contextMenus — To provide a right-click "Save to LayerGlyph" menu item.
- alarms — To run periodic Kindle sync in the background.
- activeTab — To access the current tab only when you interact with the extension.
- offscreen — To run a local, on-device AI model for auto-tagging (the model runs entirely in your browser; nothing is sent to a server for this feature).
- notifications — To show sync-completion and background-task status notifications.
- downloads — To save your local JSON backup file to disk when you use the export/backup feature. This writes a file to your device; it does not upload anything.
- read.amazon.*/notebook — To read your Kindle highlight data from Amazon's notebook page while you are logged in.
- All URLs (https://*/*) — To enable the text highlight and bookmark button on any web page you visit. Page content is only read and stored locally when you explicitly save a highlight or bookmark — we do not continuously monitor or transmit your browsing.
9. Third-Party Services
- Google OAuth — Used only if you optionally sign in (currently for the Notion export feature). Governed by Google's Privacy Policy.
- Supabase — Optional account authentication infrastructure only, as described in Section 4.
- Notion — Only contacted if you explicitly use the optional Notion export feature, to create pages in your own Notion workspace.
- Amazon Kindle — Highlight data is fetched from your Amazon session. We do not store your Amazon credentials.
- Amazon product links — Clicking a book cover or "buy" link takes you to Amazon via an affiliate link, opening Amazon's own site in your browser. We do not scrape prices, reviews, ratings, or stock data from Amazon.
- Catalog CDN — Book search/recommendation metadata (titles, authors, covers) is fetched from a static content delivery network. This is read-only lookup traffic; it does not include your highlights, notes, or reviews.
10. Data Deletion
You can delete individual highlights, books, reviews, or bookmarks at any time directly from the LayerGlyph interface — this removes them from your device's local storage. If you signed in with Google, you can request deletion of your account by emailing us at yutaro.private@gmail.com.