Not a suite of cloud apps. An operating system that runs in your browser.
A web OS is a complete operating system that runs inside a browser tab: a desktop with a window manager, a real file system, multitasking, and native applications that live and work together — no install, no local machine dependency. UltimaOS is a web OS built for one thing the others are not: sovereignty. Every window, every file, every app runs inside a single post-quantum encrypted, EU-hosted environment. The apps are not the product — the operating system is. Mail, chat, files, documents and AI are simply the citizens that live in it, sharing one identity, one encrypted file system, and one cryptographic boundary.
Google Workspace or Microsoft 365 are collections of separate cloud products glued together by single sign-on. A web OS is the opposite: one operating system where every app runs inside the same desktop, shares the same file system, and inherits the same guarantees. There are no silos to reconcile — there is one machine.
Windows you can move, resize, tile and layer. A taskbar and launcher. Drag-and-drop between apps. A file manager that owns your data. UltimaOS behaves like the operating system you already know — it just happens to run in a tab, on any device, with nothing to install.
Because it is an operating system, encryption is not a per-app feature — it is the boundary of the whole environment. Post-quantum key exchange and end-to-end encryption apply to every window by default, not just to email. No app inside UltimaOS can leak outside that boundary.
Web operating systems already exist — Puter, daedalOS, OS.js. UltimaOS is the one built for production work under real sovereignty and post-quantum threat models.
Key exchange uses ML-KEM-768 and signatures use ML-DSA-65 — the NIST-standardised post-quantum algorithms (FIPS 203 and 204). Your data is protected today against the harvest-now-decrypt-later threat, at the operating-system level, for every app.
Data is encrypted on your device before it reaches the server. There is no central database of passwords to breach, and no server-side key that could decrypt your workspace. UltimaOS cannot read your files — by design, not by policy.
The entire OS runs on European infrastructure under EU jurisdiction. No CLOUD Act exposure, no transatlantic data transfer, GDPR-aligned by architecture rather than by a checkbox. Sovereignty is a property of the operating system, not an add-on tier.
Where most browser operating systems are demos or developer playgrounds, UltimaOS ships a real, daily-driver set of apps — mail, chat, files, documents, spreadsheets, boards, notes, calendar, contacts and AI — all native to the OS and designed to be lived in.
A single cryptographic identity unlocks the whole environment. No per-app accounts, no scattered permissions, no reconciling who has access to what across five products.
Every app reads and writes to the same encrypted file system. A file created in documents opens in the file manager, attaches in mail, and shares in chat — without ever leaving the encrypted boundary or being copied into a separate silo.
The post-quantum, end-to-end encrypted perimeter is the operating system itself. A bundle of SaaS apps has as many boundaries as it has products; an OS has one. That is the difference between hoping every vendor got it right and knowing the environment did.
Because the OS lives in the browser, your desktop, files and apps are the same on any machine you sign into — with nothing stored locally and nothing to install. Close the tab and the environment is gone from the device; open it anywhere and it is exactly as you left it.
Short answer
A web OS is a full operating system that runs inside a browser: a desktop environment with a window manager, a file system, multitasking, and native applications, requiring no local installation. UltimaOS is a web OS that adds post-quantum encryption and EU sovereignty as properties of the operating system itself.
Short answer
Google Workspace and Microsoft 365 are bundles of separate cloud applications connected by single sign-on. UltimaOS is a single operating system in which the apps live together, sharing one identity, one encrypted file system and one post-quantum boundary. It is an OS, not a suite.
Short answer
No. UltimaOS runs entirely in your browser on any device. There is nothing to install and nothing stored locally — your desktop, files and apps live inside the encrypted OS and follow you to any machine you sign into.
Short answer
UltimaOS encrypts data end-to-end on your device before it reaches the server, uses NIST post-quantum algorithms (ML-KEM-768 and ML-DSA-65) for key exchange and signatures, keeps no password database, and runs entirely on EU infrastructure. Security is enforced at the OS layer, so every app inherits it.
Short answer
Puter, daedalOS and OS.js are pioneering web operating systems, largely open-source and developer-oriented. UltimaOS is built for production work under a sovereignty and post-quantum threat model: end-to-end encrypted, EU-hosted, with a full suite of daily-driver apps native to the OS.
No ads, no data mining, no trial clock. Individual and family accounts are free — permanently. Organisations pay per seat, and that is what funds it.