Privacy Policy

Last updated: March 1, 2026

Second Brain ("the App") is a personal knowledge management application. This policy explains what data we access, how we use it, and how you can control it.

1. Data We Access

When you connect your Google account, the App requests access to:

• Google Drive (read-only): We read your documents to build your persona profile, detect projects, and analyze your writing style.
• Google Drive (app-created files): We create and manage a "Second Brain" folder in your Drive to sync your notes and project files.
• Gmail (read-only): We read your email messages to provide context for your AI assistant and help with email-related tasks.
• Gmail (send): We send emails and create drafts on your behalf when you ask the AI assistant to do so.

On macOS, the App may also access Apple Calendar, Apple Mail, iMessage, and local files if you grant permission through the operating system.

2. How We Use Your Data

Your data is used to:

• Build a personal profile ("persona") that helps the AI assistant understand you
• Detect and organize your active projects
• Analyze your writing style so the AI can write in your voice
• Sync your Second Brain notes to Google Drive
• Provide context to the AI assistant for conversations and tasks

3. How We Store Your Data

Second Brain runs locally on your computer. All data is stored on your machine in the ~/.second-brain/ directory, including your Google OAuth tokens and application configuration. Your notes and project files are stored in the ~/SecondBrain/ directory.

We do not operate servers that store your personal data. There is no cloud database of your documents, emails, or messages.

4. Third-Party Data Processing

To power the AI assistant, portions of your data (such as document excerpts, email content, and conversation context) are sent to Anthropic's Claude API for processing. This data is sent over encrypted connections and is subject to Anthropic's Privacy Policy. Anthropic does not use API inputs to train their models.

No other third parties receive your data.

5. Data Retention

Since all data is stored locally on your device, it persists until you delete it. Data sent to Anthropic's API for processing is not retained by Anthropic beyond the duration of the API request, per their data usage policy.

6. How to Delete Your Data

You can delete all locally stored data at any time by:

• Deleting the ~/.second-brain/ folder (configuration, tokens, and app data)
• Deleting the ~/SecondBrain/ folder (your notes and files)

To revoke the App's access to your Google account:

• Visit myaccount.google.com/permissions
• Find "Second Brain" and click "Remove Access"

7. Children's Privacy

The App is not directed at children under 13 and we do not knowingly collect data from children.

8. Changes to This Policy

We may update this policy from time to time. Changes will be posted on this page with an updated date.

9. Contact

If you have questions about this privacy policy, please contact us at: danyang.zhao@gmail.com