Effective July 3, 2026

Privacy policy.

Deep Shadow is a Chrome extension for practicing English rhythm and intonation with captioned videos. It works without an account or advertising. Users may choose to share limited anonymous usage and technical diagnostics to help improve reliability and the practice experience.

Information processed

Deep Shadow processes the following information only to provide its visible practice features:

• The active YouTube page URL, video title, caption text and timings, and current playback state.
• YouTube tab audio while the user enables optional Precise timing, processed transiently to refine the active phrase’s start and end.
• Microphone audio captured after the user explicitly enables microphone access and only during the learner’s speaking turn.

If anonymous diagnostics are enabled, Deep Shadow also processes:

• A random diagnostics identifier generated by the extension, not derived from a name, email, Google account, device identifier, or advertising identifier.
• Coarse feature-use, performance, and categorized outcome events.
• Technical exceptions with a sanitized message, extension code stack trace, version, component, operation, and sanitized lifecycle checkpoints.

Anonymous diagnostics never include YouTube URLs, video IDs, titles, captions, phrase text, tab or command IDs, microphone recordings, YouTube tab audio, audio levels, refined timestamps, or recording metadata.

How information is used

Video information is used to divide captions into phrases, control the selected phrase’s playback, show the current title and captions, and restore the video when practice ends. When Precise timing is enabled, YouTube tab audio levels are analyzed locally while selected phrases play, and the captured stream is relayed locally to the default audio output. Microphone audio is captured only during the learner’s speaking turn, released before comparison playback, and used to play the learner’s take immediately after the original phrase so the learner can compare them.

Anonymous diagnostics are used only to measure activation and feature use, diagnose reliability and performance, understand aggregate retention, and investigate extension errors. They are not used for advertising, profiling, or decisions about an individual.

Local processing and retention

YouTube tab audio is analyzed as selected phrases play and is not recorded or retained; only refined start and end timestamps remain in memory for the active video session. Microphone audio remains in memory on the user’s device. It is played for the active comparison and discarded after the repetition or when the practice session ends. Deep Shadow does not save voice history. Captions, video titles, URLs, playback state, and refined timestamps are not stored by Deep Shadow after the active session.

When diagnostics are enabled, the random diagnostics identifier and consent choice are stored locally. Disabling diagnostics removes the optional network permission, clears pending events, and deletes the local identifier. Diagnostic events and exceptions are retained by the analytics processor for no more than 13 months.

Network use and sharing

Deep Shadow communicates directly with YouTube over HTTPS to load the selected video page and caption data. If the user enables anonymous diagnostics, the extension sends only the categories described above over HTTPS to PostHog’s US-hosted service, which acts as a data processor. IP and GeoIP enrichment are disabled. Information is not sold, shared for advertising, transferred for unrelated purposes, or used to determine creditworthiness.

Permissions

• Side panel: displays the listen, speak, compare, and playback controls beside the active video.
• Active tab: allows a toolbar click to open Deep Shadow for the selected YouTube tab.
• Local storage: remembers practice preferences, diagnostics consent, and—only while diagnostics are enabled—the random diagnostics ID and a short-lived retry queue.
• Local preferences: remembers whether Precise timing should resume after reopening the panel. This data stays in Chrome on the user’s device and requires no additional extension permission.
• Tab capture (optional): analyzes the selected YouTube tab’s audio locally for cleaner phrase boundaries while Precise timing is enabled. Audio is not recorded, saved, or uploaded.
• YouTube site access: reads captions and controls playback only on YouTube pages so the user can practice one phrase at a time.
• Microphone: records the learner only during a speaking turn for immediate on-device playback and comparison. Audio is not uploaded or saved.
• Anonymous diagnostics host (optional): after a one-click disclosure, sends limited anonymous usage and technical diagnostics to us.i.posthog.com. Declining does not affect practice features.

Users can turn off anonymous diagnostics or Precise timing in the side panel, revoke optional permissions through Chrome settings, disable YouTube site access, disable the extension, or uninstall it at any time. The panel can copy the random diagnostics ID for a support or deletion request.

Chrome Web Store Limited Use

Deep Shadow’s use of information received from Google APIs will adhere to the Chrome Web Store User Data Policy, including the Limited Use requirements.

Security

Deep Shadow contains its executable logic in the installed extension package and does not load remote executable code. Required network requests use HTTPS. The diagnostics SDK is bundled locally; session replay, automatic click and page capture, surveys, remote feature flags, and console-log capture are disabled. Payloads pass through an event and property allowlist before transmission.

Changes and support

Material changes to this policy will be published at this URL with an updated effective date and reflected in the Chrome Web Store privacy declarations. For questions, deletion requests, or privacy requests, include the diagnostics ID when available and use the Deep Shadow support page.

YouTube is a trademark of Google LLC. Deep Shadow is not affiliated with or endorsed by YouTube or Google.