Lumo is an open-source, privacy-focused artificial intelligence assistant developed by Proton AG, which is primarily owned by the non-profit Proton Foundation. The service is designed to prioritize user privacy, operating without logs, employing zero-access encryption, and not using user data for model training.[1]
Lumo was created by Proton, the Swiss company behind services such as Proton Mail, Proton VPN, Proton Pass, and Proton Drive.[2][3][1][4] Development was led by Proton’s Machine Learning team.[5] The product was officially launched on 23 July 2025.[6][7] On 21 August 2025, Proton released version 1.1, which included performance improvements and upgraded models to enable more complex requests.[5][8] On 16 October, Proton released version 1.2, which included dark mode, bug fixes and chat personalisation.[9] On 30 October, Proton released their Lumo for Business plan, which is a large scale AI platform for business and is integrated with Proton Business Suite.[10]
Features
Lumo allows users to summarize documents, generate code, and compose text.[11] It incorporates privacy measures consistent with Proton’s other services. Conversations are not logged, and chats are stored with zero-access encryption so that no one except the user (not even Proton) can access the data.[6] The system does not use conversations to train the large language models. Lumo’s mobile app and web app code is fully open source and built on publicly available models, enabling external verification of its security.[2][12][13]
The service operates under European data protection laws and allows users to delete their data. Proton AG is headquartered in Switzerland, where data protection laws are governed by the Swiss Federal Data Protection Act (FADP). Switzerland’s privacy legislation and independence from European Union and United States jurisdictions limit the scope of government surveillance requests and legal requirements for data access and disclosure.[3]
Lumo integrates with Proton Drive, allowing users to upload and manage files directly from their Drive storage for use in chats. Files added through this integration appear in the chat’s working memory, known as chat knowledge.[14]
The assistant can be used without an account. Creating a Proton account enables access to encrypted chat histories.[1][15]
It is available as a web application and through iOS and Android mobile apps.[16][6][17]
Reception
PCMag described Lumo as a "ChatGPT alternative" that is focused on privacy.[16]
TechRadar wrote that Proton had created "a super secure and private AI chatbot," highlighting it as a safer choice for handling confidential information.[2]TechCrunch reported that Lumo “encrypts all chats, and keeps no logs.”
Tom’s Hardware wrote that Lumo’s “real innovation lies in the zero-access encryption system, which guarantees users an exclusive decryption key. This mechanism prevents third parties, including Proton itself, from accessing content generated or processed by the virtual assistant. Data is stored locally on users' devices, creating an impenetrable technical barrier for governments, advertisers and anyone else who wants to access personal information.”[12]
Engadget similarly emphasized that "not even Proton can view your chats. As a result, the company can't share your data with governments, advertisers or, for that matter, any other company, and it can't use your data to train future AI models."[1]
In October, Lumo spotlighted by TIME Magazine among “The Best Inventions of 2025: Special Mentions.”[18]
↑TIME Staff (2025). "Proton Lumo". TIME. TIME USA, LLC. Retrieved 2025-11-04.
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