Lumo is the AI assistant from Proton, the Swiss company behind Proton Mail and Proton VPN. Its selling point is not that it is the cleverest chatbot on the market, and Proton does not pretend it is. It is that your conversations are encrypted so that Proton cannot read them, they are not logged, and they are never used to train a model. For a growing number of people pasting payslips, medical letters and work documents into AI tools, that is the feature that matters.
Lumo deal: 23% off Lumo Plus on annual billing
- Offer: Lumo Plus at US$9.99 a month (£7.50 / €8.90), billed US$119.88 (£89.96 / €106.77) every 12 months
- Promo Code: No Promo Code needed; the annual discount is shown on Lumo’s pricing page
- Who qualifies: anyone buying Lumo Plus direct from Proton on a 12-month plan
- Key terms: discounted from US$12.99 a month (£9.75 / €11.57). 30-day money-back guarantee. Cancel any time; Plus features end with the billing period.
| Offer detail | What you get |
|---|---|
| Promo Code | No Promo Code needed |
| Welcome offer | 23% off Lumo Plus on annual billing: US$9.99 a month (£7.50 / €8.90), saving US$36 (£27.01 / €32.06) a year |
| Who qualifies | Anyone buying Lumo Plus direct from Proton on the 12-month plan; the free tier is open to all |
| Key terms | Billed US$119.88 (£89.96 / €106.77) every 12 months; no cancellation fees; 30-day money-back guarantee |
| How to claim | Open Lumo’s pricing page, choose Lumo Plus on yearly billing, sign in or create a Proton account and pay |
Lumo: key facts
- Official website: lumo.proton.me
- Owner: Proton AG (primary shareholder: the non-profit Proton Foundation)
- Headquarters: Plan-les-Ouates, Geneva, Switzerland
- Founded: July 2025 (Lumo launch); Proton AG 2014
- Ratings: App Store 3.6 (33 ratings, Polish App Store)
- Headline offer: 23% off Lumo Plus on annual billing: US$9.99 a month, billed US$119.88 a year
- Promo Code: No Promo Code needed
- Price from: Free; Lumo Plus from US$9.99 a month (£7.50 / €8.90) on annual billing
- Free plan or trial: Yes: usable without an account; free Proton account adds encrypted history; limited Max model use, messages and image generations, 1 Project
- Payment methods: Visa, Mastercard, American Express, PayPal, Bitcoin (account credit), Cash (account credit), Bank transfer (account credit)
- Best features: Zero-access encrypted chat history, no logs, no training on chats; Ghost mode, web search with cited sources, file and image analysis; Built and hosted in Europe on open-source models
Lumo at a glance
- Price from: free; Lumo Plus from US$9.99 a month (£7.50 / €8.90) on annual billing
- Free tier: yes, usable without an account, with more messages and saved history once you sign in
- Lumo Plus: more use of the most capable model, more messages, unlimited Projects and Custom Lumos
- Privacy: zero-access encrypted chat history, no logs, no training on your chats
- Hosting: built and hosted in Europe on Proton-controlled servers
- Platforms: web at lumo.proton.me, iOS and Android
- Launched: July 2025
- App rating: 3.6/5 from 33 ratings on the Polish App Store
What Lumo is, and who owns it
Lumo is a chat assistant made by Proton AG, the Geneva company whose main shareholder is the non-profit Proton Foundation. It launched in July 2025 and received a significant update, Lumo 1.1, the following month. It does the jobs you would expect: drafting emails, summarising documents, explaining concepts, answering questions with web search and, in its newer versions, creating and editing images.
The difference is under the bonnet. Lumo runs on open-source language models rather than a proprietary one, on servers Proton controls in Europe. In August 2025, Proton’s chief executive, Andy Yen, said proposed changes to Swiss surveillance rules had led the company to choose Germany to host Lumo’s servers, making it the first Proton product to move infrastructure out of Switzerland. Proton says Lumo still operates under Swiss legal protections.
Lumo prices: every plan explained
Prices below are Proton’s US dollar figures, with sterling and euro conversions. Lumo’s pricing page can also show euros and Swiss francs.
| Plan | Price | What you get |
|---|---|---|
| Lumo Free | Free | Limited use of the most capable model, limited messages and chat history, limited image generations, one Project, web search, small file uploads |
| Lumo Plus, monthly | US$12.99 (£9.75 / €11.57) a month | More use of the most capable model, more messages and extended history, more image generations, unlimited Projects and Custom Lumos, multiple large file uploads |
| Lumo Plus, annual | US$9.99 (£7.50 / €8.90) a month, US$119.88 (£89.96 / €106.77) billed | As above, 23% cheaper |
| Lumo for Business | US$11.99 (£9.00 / €10.68) per user a month, billed annually | Business version, also available within Proton Workspace |
Lumo Free is open to anyone, and you can start a chat without creating an account. Signing in with a free Proton account unlocks encrypted chat history and more messages. Proton does not publish exact message caps, and reviewers have found the free limits tight for daily heavy use.
Lumo Plus is aimed at people who use an assistant every working day. The key upgrades are more access to the “Max” model, which handles harder reasoning, unlimited Projects for grouping chats and files, and Custom Lumos, which are assistants set up with your own instructions.
Bundles. Proton Unlimited, Duo and Family include Lumo Free, not Lumo Plus. The only Proton bundle that includes Lumo Plus is Proton Visionary, listed on Proton’s plans page at €39.99 a month or €359.88 a year, which also covers six users and 6TB of storage.
A worked example: what you really save
Take a solicitor’s assistant in Leeds who wants an AI helper for tidying letters and summarising long PDFs, and does not want client details sitting in someone else’s training data.
- Lumo Plus paid monthly costs US$155.88 (£116.97 / €138.83) a year.
- Lumo Plus on annual billing costs US$119.88 (£89.96 / €106.77), a saving of US$36 (£27.01 / €32.06).
- ChatGPT Plus and Claude Pro are each US$20 a month (£15.01 / €17.81) on monthly billing, or US$240 (£180.10 / €213.74) a year, so annual Lumo Plus costs half as much as a year of either paid monthly.
Whether that saving is worth it depends on the work. For letters and summaries, Lumo is capable. For long, analytical reports or complex coding, the more expensive rivals are stronger.
Free tier, trials and discounts
There is no free trial of Lumo Plus as such, because the free tier does that job: you can use Lumo without an account, then with a free one, before deciding to pay. Paid plans carry a 30-day money-back guarantee.
Proton does not publish Promo Codes for Lumo, and its student scheme, run through Student Beans for Proton Mail, Drive, VPN and Unlimited, does not list Lumo. Proton has run Black Friday sales on its main bundles in recent years, so it is worth checking the pricing page in November.
Key features
- Zero-access encryption for saved chat history, and encryption of messages between your device and Lumo
- No logs and no training: Proton says Lumo never logs your data and your chats are never used to train AI
- Ghost mode, which deletes a conversation once you close it
- Web search with cited sources, switched on when you need current information
- File analysis for PDFs and images, including files pulled from Proton Drive
- Image creation and editing
- Fast and Thinking modes, for quick answers or multi-step reasoning
- Memory, Projects and Custom Lumos for organising work and repeat tasks
Platforms and availability
Lumo runs in the browser at lumo.proton.me and has apps for iOS and Android. Proton says the apps are open source. A free Proton account gives you Lumo alongside Proton Mail, Drive, Pass and VPN under one login.
How to sign up and use Lumo
- Go to lumo.proton.me and start typing; no account is needed for a first try.
- Create a free Proton account, or sign in with an existing one, to save encrypted history.
- Switch on web search when you need current facts, and check the cited sources.
- Use Ghost mode for anything you would rather not keep, such as a medical question.
- Upload a PDF or image, or attach one from Proton Drive, and ask for a summary.
- If you hit the limits, upgrade to Lumo Plus from the pricing page, choosing yearly billing for the lower price.
A sensible routine for a freelancer: keep a Project for each client, set up a Custom Lumo with your house style, and use Ghost mode for anything involving personal data you do not need to revisit.
Privacy and security
Privacy is the reason Lumo exists. Proton says chats are protected in transit by bidirectional asymmetric encryption and saved history uses zero-access encryption, so Proton cannot read it. It also says Lumo keeps no logs, whether or not Ghost mode is on, and that conversations are never used to train AI or shared for advertising.
Two points of context are worth adding. First, ChatGPT and Gemini now let you opt out of training and turn off chat history, so the gap is narrower than it was. What Lumo adds is encryption that keeps Proton itself out. Second, Proton names “open-source models” without listing which ones on its main pages, so you are trusting Proton’s description of the stack.
App ratings and customer service
Lumo AI by Proton scores 3.6 out of 5 from 33 ratings on the Polish App Store, a small sample. Support runs through Proton’s help centre at proton.me/support, and Lumo Plus subscribers get the same paid-plan support as other Proton customers.
What users and reviewers say
Lumo is young, so verified user reviews are thin, and the professional press gives the clearer picture. TechRadar’s review in July 2026 concluded that Lumo delivers on its promise of AI chat that not even Proton can read, but that its output still trails frontier models. It found Lumo competent at summarising documents, drafting short emails and explaining concepts, but weaker on longer structured work and analytical questions than ChatGPT Plus and Claude, and it flagged tight free-tier limits.
Android Authority, testing the first version in July 2025, found it promising on privacy but described it as half-baked, with an older knowledge cut-off and missing features such as image generation. Proton has since added image creation and Thinking mode, which addresses some of those points.
Pros and cons
Pros
- Chats encrypted so Proton cannot read them, with no logs and no training on your data
- Usable free, even without an account
- Lumo Plus costs less than ChatGPT Plus or Claude Pro
- Hosted in Europe, run by a company with a strong privacy record
- Integrates with Proton Drive for file analysis
Cons
- Answers trail the leading models on complex, analytical tasks
- Free limits are tight and not published in detail
- Lumo Plus is not included in Unlimited, Duo or Family
- Proton does not name the underlying models on its main pages
- Small number of app store ratings so far
Lumo vs ChatGPT vs Claude vs Le Chat
| Lumo | ChatGPT | Claude | Le Chat | |
|---|---|---|---|---|
| Maker | Proton (Switzerland) | OpenAI (US) | Anthropic (US) | Mistral AI (France) |
| Free tier | Yes, no account needed | Yes | Yes | Yes |
| Main paid plan | Lumo Plus, US$12.99 a month (£9.75 / €11.57), or US$9.99 a month on annual billing | ChatGPT Plus, US$20 a month (£15.01 / €17.81) | Claude Pro, US$20 a month (£15.01 / €17.81) | Le Chat Pro |
| Zero-access encrypted history | Yes | No | No | No |
| Models | Open-source | Proprietary | Proprietary | Mistral’s own, some open-weight |
ChatGPT remains the capability benchmark, and both ChatGPT and Claude are stronger than Lumo on long, analytical work. Le Chat, from Paris-based Mistral, is the closest European rival, though it does not offer Lumo’s zero-access encryption. Lumo wins on one axis, privacy, and it is a clear win. For a different take on a privacy-first assistant, see our Lorka AI review.
Lumo FAQs
Is there a Lumo promo code?
No Promo Code is needed. The saving is annual billing, which takes Lumo Plus from US$12.99 to US$9.99 a month (£7.50 / €8.90), 23% off.
Is Lumo free?
Yes. You can use Lumo without an account, and a free Proton account adds saved, encrypted chat history and more messages.
How much is Lumo Plus?
US$12.99 a month (£9.75 / €11.57) on monthly billing, or US$119.88 (£89.96 / €106.77) a year.
Is Lumo included in Proton Unlimited?
Proton Unlimited, Duo and Family include Lumo Free. Lumo Plus is included only in Proton Visionary.
Does Lumo train on my data?
No. Proton says conversations are never used to train AI and that Lumo keeps no logs.
Is Lumo safe for work documents?
Its encryption and no-logs policy make it one of the more private options. Check your employer’s rules first; Proton also sells Lumo for Business.
What is Ghost mode in Lumo?
A private session in which the conversation is deleted once you close it.
Is Lumo better than ChatGPT?
For privacy, yes. For capability on complex tasks, ChatGPT and Claude are ahead.
Where is Lumo hosted?
Proton says Lumo is built and hosted in Europe on Proton-controlled servers. Its chief executive has said those servers are in Germany.
Verdict
Lumo is the AI assistant to choose when you would rather nobody, including the company that runs it, could read your conversations. For everyday jobs, from drafting a polite complaint to a letting agent to summarising a 40-page policy document, it does well enough that most people will not miss the extra horsepower of the market leaders. Lumo Plus is fairly priced, especially on annual billing. If your work leans on deep analysis or long-form reasoning, keep a mainstream assistant for that and use Lumo for anything personal.
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