Privacy Policy for Second Brain

Second Brain is designed to be private. The core philosophy is that your data belongs to you. The application's primary function is to scan files in a directory you specify (your "Sync Directory") and create a private, offline search index. This index, along with all application settings and configuration files, are stored entirely on your local computer, in a local AppData folder called "Second Brain" (you can open this in Settings). By default, no data whatsoever is collected or transmitted by Second Brain.

The application only connects to external services when you explicitly configure it to do so. These user-controlled connections are as follows:

AI Mode (OpenAI): If you enable "AI Mode" and select the "OpenAI" backend, then your search query, relevant text snippets from your local files, and any attachment content are sent to the OpenAI API to generate a response. This usage is subject to OpenAI's privacy policy. Second Brain encrypts your API key and stores it securely and locally using the Windows Credential Manager. At any time, the API key can be removed in Settings.

AI Mode (LM Studio): If you select the "LM Studio" backend, all AI processing occurs on your local machine. No data is sent to any external service.

Model Downloads: The app comes with two small, open-source embedding models pre-installed. When you select another one, the application connects to Hugging Face (a public model repository) to download the open-source embedding models and saves the model weights to the local AppData files. This download does not involve sending any of your personal data.

In summary, your personal files and search index never leave your device unless you actively enable an optional, third-party connection (OpenAI). The LM Studio backend is a 100% offline AI experience, as is basic search with AI Mode turned off.

Skeptical? Take a look at the open source code: https://github.com/henrydaum/second-brain.