Most AI assistants have a privacy problem. When you use ChatGPT, Gemini or Copilot your conversations are processed on company servers, potentially used to train future models and subject to data requests from governments. For most everyday tasks that’s an acceptable trade off. For sensitive personal or professional conversations it’s a genuine concern.
Lumo is Proton’s answer to that problem. Built by the Swiss company behind Proton Mail and Proton VPN — services trusted by over 100 million people specifically because of their privacy credentials — Lumo brings the same privacy first approach to AI.
This is our honest review.
What is Lumo?
Lumo is a privacy focused AI assistant developed by Proton AG and launched in July 2025. It’s available on web, iOS and Android and is designed as a direct alternative to mainstream AI tools like ChatGPT and Gemini — with one fundamental difference: your conversations are fully encrypted and completely private.
Even Proton itself cannot read your chats.
How Does Lumo Protect Your Privacy?
This is what makes Lumo genuinely different from every other mainstream AI assistant:
Zero access encryption — your conversations are encrypted end to end. Proton has no access to your chat history and cannot read your conversations even if legally compelled to hand over data.
No training on your data — Lumo never uses your conversations to train its AI models. What you say stays with you.
No server logs — Lumo operates without keeping logs of your conversations on its servers.
Swiss jurisdiction — Proton is based in Switzerland which sits outside the Five Eyes, Nine Eyes and Fourteen Eyes intelligence sharing alliances. This means your data is subject to strong Swiss privacy law rather than US or UK government data access frameworks.
Open source models — Lumo is powered by open source AI models including Mistral Nemo and OLMO 2 — meaning anyone can inspect the underlying technology and verify Proton’s privacy claims.
Ghost mode — a one time chat feature that leaves absolutely no trace of the conversation even on your own device.
What Can Lumo Actually Do?
Lumo handles the core tasks you’d expect from any AI assistant:
- Writing and editing documents
- Summarising long texts and files
- Answering questions and research assistance
- Web search through privacy friendly search engines
- File analysis — upload documents for Lumo to read and summarise
- Integration with Proton Drive — work with your encrypted files directly
- Code writing and debugging
The web search feature is worth noting — it’s disabled by default to maximise privacy but can be enabled when you need current information.
How Does Lumo Compare to ChatGPT and Claude?
This is the honest question most people want answered. Here’s the straightforward comparison:
Privacy — Lumo wins decisively. No other mainstream AI assistant offers the same level of encryption and data protection. If privacy matters to you Lumo has no real competition.
Raw capability — ChatGPT and Claude are currently more capable for complex reasoning, nuanced writing and advanced tasks. Lumo is powered by open source models that are good but not yet at the level of GPT-5.5 or Claude Opus.
Ecosystem integration — if you already use Proton Mail, Proton Drive and Proton VPN the integration is seamless and genuinely useful. If you don’t use Proton’s ecosystem the integration benefit is limited.
Real time information — Lumo can search the web when enabled but it’s not as smooth as tools built with web search as a core feature.
Price — Lumo’s free plan is genuinely useful. The paid plan is competitive with alternatives.
| Feature | Lumo | Claude | ChatGPT | Gemini |
|---|---|---|---|---|
| Privacy | ⭐⭐⭐⭐⭐ | ⭐⭐⭐⭐ | ⭐⭐⭐ | ⭐⭐⭐ |
| Capability | ⭐⭐⭐ | ⭐⭐⭐⭐⭐ | ⭐⭐⭐⭐⭐ | ⭐⭐⭐⭐ |
| Free plan | ✅ | ✅ | ✅ | ✅ |
| Data training | ❌ Never | ⚠️ Opt out | ⚠️ Opt out | ⚠️ Opt out |
| Jurisdiction | Switzerland | USA | USA | USA |
| Encryption | ✅ End to end | ❌ | ❌ | ❌ |
Lumo Pricing
- Free plan — available with core features included
- Lumo Plus — £10/month ($12.99/month) — unlimited chats, larger file uploads and expanded features
Lumo is also available as part of Proton’s broader ecosystem plans if you use multiple Proton services.
Lumo for Business
Proton launched Lumo for Business specifically for organisations that need AI assistance without compromising on data security. It offers the same zero access encryption with additional team management features — making it particularly relevant for law firms, healthcare organisations, financial services and any business handling sensitive client data.
The zero access encryption means that even within an organisation only the individual user can access their own conversations — administrators cannot read employee chats.
Who Should Use Lumo?
Privacy conscious individuals — if you’re uncomfortable with Big Tech AI companies processing your conversations Lumo is the most credible alternative available.
Legal and healthcare professionals — client confidentiality is a professional obligation. Lumo’s encryption makes it significantly safer for sensitive professional conversations than mainstream alternatives.
Journalists and activists — anyone whose conversations could put them or their sources at risk benefits from Lumo’s Swiss jurisdiction and zero access encryption.
Existing Proton users — if you already use Proton Mail, Drive or VPN adding Lumo to your workflow is seamless and keeps your entire digital life within one privacy focused ecosystem.
Who might prefer alternatives:
If raw capability is your priority and privacy is less of a concern — Claude and ChatGPT are currently more powerful for complex tasks. If you’re in Google’s ecosystem Gemini offers better integration. If you’re a Microsoft Office user Copilot is the more practical choice.
What About Proton VPN?
Proton VPN is one of the most trusted VPN services available — and pairs naturally with Lumo if privacy is your priority. Using Lumo alongside Proton VPN means both your AI conversations and your internet connection are protected under Swiss privacy law.
For maximum privacy the combination of Lumo and NordVPN or Proton VPN is worth considering — encrypting both your AI interactions and your broader internet activity.
The Honest Verdict
Lumo is a genuinely impressive privacy focused AI assistant. It does exactly what it promises — your conversations are private, encrypted and never used to train AI models. For users who prioritise privacy over raw capability it’s the most credible AI assistant available in 2026.
The trade off is capability — Lumo isn’t yet as powerful as Claude or ChatGPT for complex tasks. But for everyday AI assistance where privacy matters Lumo is worth serious consideration.
Start with the free plan at lumo.proton.me and see whether the privacy benefits justify switching from your current AI tool.
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For privacy conscious users:
- Noise Cancelling Headphones — ideal for private conversations and focused work sessions with Lumo
- Co-Intelligence by Ethan Mollick — the best guide to understanding AI tools and making informed choices about which ones to trust
- The Coming Wave by Mustafa Suleyman — essential reading for understanding the privacy and safety implications of AI
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