Lumo
Proton's AI assistant, built on the same promise as Proton Mail: your conversations stay encrypted, unlogged, and provably out of reach — including from Proton itself.
What is Lumo?
Proton built its name on Proton Mail and Proton VPN, so when the Swiss company launched an AI assistant in July 2025, it made sense that privacy would be the entire pitch rather than a bullet point. Lumo runs on zero-access encryption, keeps no server-side logs of your conversations, and never uses your prompts to train its models — and unlike most privacy claims in tech, this one is checkable: Lumo is fully open source, so anyone can inspect the code and verify it does what Proton says.
Lumo grew fast for a privacy-first product — more than 10 million people had started using it within a year of launch. In June 2026, Lumo 2.0 rebuilt the assistant on new architecture with Fast and Thinking modes, multimodal input, user-controlled memory, and encrypted Projects, closing a lot of the capability gap with mainstream competitors. Proton has also been moving Lumo's infrastructure out of Switzerland and into the EU proper, an investment of more than €100 million, after concerns about Swiss government surveillance proposals that would be illegal under EU law.
User figures and investment amount are Proton's own disclosed numbers as of its Lumo 2.0 announcement, June 2026. Figures may be updated by Proton over time.
Key features
Zero-access encryption
Conversations are encrypted such that not even Proton can read them — a stronger guarantee than most competitors offer.
No logs, no training
Nothing is stored server-side, and prompts are never used to improve future models.
Guest & Tor access
Usable anonymously with no account and no sign-up, including over the Tor network.
Encrypted Projects
Dedicated, still-encrypted spaces for organizing an ongoing task's chats and files.
Fast & Thinking modes
Switch between quick replies and slower, more deliberate reasoning depending on the task.
Proton Drive integration
Analyze files directly from encrypted Proton Drive storage without leaving the privacy boundary.
Pricing
Free
- No account needed — guest & Tor access supported
- Zero-access encryption on every chat
- Limited daily usage
Lumo Plus
- Unlimited chats & priority access to fastest models
- Encrypted Projects & advanced image generation
- Note: not included in Proton Unlimited by default
Lumo for Business
- Secure team collaboration features
- Admin controls & centralized management
- Same zero-access, no-logs guarantees
Existing Proton Unlimited subscribers only get the free Lumo tier by default — Plus is a separate purchase. Some users report the price feels steep relative to raw capability compared to mainstream chatbots. Prices reflect Proton's published pricing as of July 2026 and may change.
Available models
Lumo runs on open-source language models that Proton optimizes and hosts itself, rather than a single proprietary model — consistent with its broader emphasis on transparency.
Integrations & platforms
Pros, cons & best for
Pros
- Privacy claims are open source and independently verifiable
- Usable completely anonymously, with no account required
- European infrastructure with a real, ongoing privacy investment
Cons
- Some users find Lumo Plus expensive relative to its raw capability
- Not included free with Proton Unlimited subscriptions
- Still behind ChatGPT or Claude on the most demanding creative or coding tasks
Best for
- Privacy-conscious individuals and professionals handling sensitive material
- Existing Proton users wanting an assistant in the same ecosystem
- Anyone who wants to use AI without creating an account at all
Take a look inside
Alternatives
For other privacy-conscious options with different trade-offs:
Our verdict
Lumo delivers on a genuinely rare promise in AI: privacy claims you don't have to just trust, because the code is open for anyone to check. That matters enormously for the specific audience it's built for — people and businesses who need to keep sensitive conversations confidential, from a company whose reputation was built on exactly that. It's a harder sell as a general daily driver: Lumo 2.0 closed real ground on capability, but some users still find the Plus tier pricey for what it delivers next to ChatGPT or Claude. If privacy is your top priority and you're willing to accept a small capability gap for it, Lumo is one of the most credible options available.
FAQ
Is Lumo actually private, or is that just marketing?
It's more than marketing — Lumo is fully open source, so its zero-access encryption and no-logs claims can be independently verified by anyone who inspects the code, rather than taken purely on trust.
Do I need a Proton account to use Lumo?
No. Lumo supports guest access, including over Tor, with no sign-up required. Creating an account lets you save chat history and access more features.
Is Lumo included with Proton Unlimited?
Only the free tier. Lumo Plus is a separate purchase even for existing Proton Unlimited subscribers.
What model does Lumo use?
Proton builds Lumo on optimized open-source language models rather than a single proprietary model, with separate Fast and Thinking modes for different types of tasks.
Why is Proton moving Lumo out of Switzerland?
Proton has cited concerns about proposed Swiss government surveillance measures that would be illegal under EU law, and is investing over €100 million to move infrastructure, starting with Lumo, into the EU.
Is Lumo as capable as ChatGPT or Claude?
Lumo 2.0 narrowed the gap significantly, but independent reviews still generally place it behind the leading mainstream assistants on the most demanding creative and coding tasks.