Private by design: your books stay on your PC

What you read says a lot about you: the illness you are researching, the contract you are reviewing, the exam you are worried about. A reading app that uploads your library to its own servers learns all of that. Lumen Reader was built so that it does not need to.

What stays on your computer

• Your books and documents. Lumen reads them where they are, or keeps its library in a folder on your PC. There is no Lumen cloud and no account to create.
• Your notes, highlights and notebooks. Saved on the PC, with backups you control. If you use Obsidian, Lumen writes your notes into your own vault.
• The read-aloud voice. It runs on the computer, so the text it reads is not sent anywhere.

What can leave, and only when you ask

AI features need a model. You decide which one:

• Your own key for Claude, OpenAI, Gemini or another provider. When you use an AI feature, the passage involved goes to that provider under your account and their terms. Lumen does not sit in the middle and does not resell AI.
• A local model through Ollama or LM Studio. Everything, including the AI, stays on the PC, and it works with no internet.

Keys are stored encrypted by Windows and are never shown back on screen. The trial and licence checks run offline on the PC; nothing about your reading is sent to us.

Built carefully

Before this release the whole program had a security review. Among other things, the review closed ways a hostile book file could have read or written files outside Lumen's own folders, and stopped web import from reaching addresses on your local network. Security work is never finished, and we will keep publishing what we fix.

The honest trade-off

Keeping everything local means there is no sync between computers and no phone app yet. If you need your library on two PCs today, a shared folder or a backup is the way. We think that is the right side of the trade for a tool that holds what you read.