Preview · open source

Write XAML.

Serve real HTML.

Web apps that load like a website: no WebAssembly, no runtime in the browser, no JavaScript to write. And native apps on Windows, macOS and Linux from the same code, with hot reload on both.

Get started See it live

Requests per second

938

Median latency

17.9 ms

Simulated traffic, computed on the server each second.

XAML saved · 28 ms

0 lines of JavaScript

Live from the server

One codebase, every screen

Web

Windows

macOS

Linux

Android · next

iOS · next

.NET 10

XAML

Aioros.Cosmo

Aioros.Pictor

Aioros.Graphs

Web

Windows

macOS

Linux

Android · next

iOS · next

.NET 10

XAML

Aioros.Cosmo

Aioros.Pictor

Aioros.Graphs

The problem

One product, two stacks

A team ships its website in one stack and its desktop app in another, or wraps the website in a web view and calls it native. Two codebases to keep in step, or one app that never feels at home.

The web app

Components and client state · an API layer for the client · a bundler and its configuration · hydration

The native app

Another UI toolkit, often another language · its own navigation and data loading · or a web view that ships a browser

With Aioros

One XAML page and its view model · loaded on the server, rendered as HTML on the web · the same page native on the desktop

One XAML, every target

The page you write is the page they get

A page is XAML with a view model. The server compiles it into a plan and answers HTML and CSS; the desktop runs the same XAML natively. The card beside the code is that code, rendered by the server you are reading.

Pages/report/Page.axaml

<c:Card> <c:CardHeader Title="Weekly report" Description="Sent every Monday to your team." /> <c:CardContent> <ToggleSwitch Content="Include charts" IsChecked="{Binding Charts}" /> </c:CardContent> <c:CardFooter> <Button Content="Save" Command="{Binding Save}" /> </c:CardFooter> </c:Card>

Weekly report

Sent every Monday to your team.

Include charts

Save

Live, from the server

Pushed while you watch

A hosted service ticks each second and invalidates a data key. Only the views that read it render again, and the server pushes them to every open page.

No WebSocket code, no client state, no JavaScript of yours.

Requests per second

938

Median latency

17.9 ms

Save the file. See the change.

The tooling a web developer expects from a serious framework, for XAML on the web and on the desktop.

Pages/Page.axaml

</StackPanel>

Edit and see

Hello, world

Hello, Aioros

Saved · 28 ms

Hot reload, both sides

A XAML edit is on screen in about 30 ms, a C# edit in about 75 ms, on the web and on the desktop, keeping scroll, focus and what you typed.

Errors at the XAML line

A failed build or a page that throws opens an overlay over the page with the file and line; fix it and the overlay goes away.

aioros dev

One command runs the app with hot reload, finds a free port and reports the build, for the web or with --desktop.

Checked at build time

Analyzers and code fixes catch what would break a page in production before it runs; a page the server cannot compile fails the build at its line.

Performance

Compiled before the first request

Pages are traced once into plans that write their HTML straight from the view models. Measured on the same machine against the same app built with each stack.

10.2×

faster than server-rendered Next.js with its cache

7.8×

faster than Blazor static server rendering

2.1×

faster than the same app in Go

4.3×

faster than the same app in Rust with Leptos

Requests per second, by page

Lumen, an issue tracker built five times; 64 connections, 4 server cores; benchmark run 241, October 2026. Geometric mean over five pages.

Everything included

What a serious framework brings

Rendering, data, motion, languages and accessibility, built in and the same on every target.

28 ms

Hot reload everywhere

Save a XAML or C# file and every open page and window updates, keeping its state.

Live by default

Invalidate a data key; the views that read it update on every screen.

Themes that follow you

Light and dark from the device, per visitor, with no flash.

Hello

Hola

你好

こんにちは

Every language

Resources per culture, an address per language, precompiled.

Tab ↹

Accessible markup

Native elements, landmarks, labels and focus, written from your XAML.

A real desktop app

Not a web view: native windows, native rendering, the same pages.

Aioros.Cosmo · shadcn/ui in XAML

Every shadcn/ui component, as XAML

All 67 components with their variants, design tokens and twelve color themes in light and dark. On the web each one is real HTML (a button is a <button>, a link an <a>); on the desktop, native controls.

67/67

shadcn/ui components ported

99.5–100%

of pixels equal to shadcn/ui's own render

color themes, light and dark

Create an account

Enter your email below to create your account.

Password

I agree to the terms

Create account

Deployed to production

Every page was compiled into a plan before the server started.

Notifications

Email digests

Push notifications

Only mentions

Make changes to your account here. Click save when you are done.

Save changes

Team members

Owner

Sofia Davis

m@example.com

Member

Jackson Lee

p@example.com

Viewer

Isabella Nguyen

i@example.com

Upload progress

Buttons and badges

Button Secondary Outline Ghost

Badge

Secondary

Outline

Destructive

Explore Cosmo

Aioros.Pictor · Recharts in XAML

Recharts' charts, with no JavaScript of yours

Recharts 2.15.4's whole API in XAML: written by the server as SVG, interactive through CSS and the framework's script, live when the server pushes new data, and drawn natively on the desktop.

chart types, every Recharts export

96×

faster than Recharts' server render

2.15.4

Recharts version whose API it follows

Area

Composed

Radar

Explore Pictor

Aioros.Graphs · d3 in C#

d3's drawing engine, byte for byte

Scales, shapes, curves, hierarchies, chords, sankeys and forces ported from d3 and tested against d3's own output: the same SVG path data, byte for byte, written by C# structs and spans with no allocation per point.

19/19

charts byte-identical to d3

2.7×

faster than d3 over those charts

3.8×

faster across 52 micro-benchmarks

Force-directed network

Partition sunburst

Chord diagram

Circle packing

Tidy tree

Streamgraph

Explore Graphs

Gallery

What you can build

Dashboards, charts, forms and drawings, each one server-rendered here and native on the desktop.

Revenue

$15,231

+20.1%

Users

2,350

+180

Active

573

+201

A dashboard with Cosmo

Charts with Pictor

Remember me

Forms with Cosmo

Drawings with Graphs

Open the gallery

Comparison

One stack instead of two

What a product team writes and keeps in step, side by side.

Web stack + desktop stack

Web view app

Aioros

Codebases to keep in step

JavaScript to write

A lot

None

Native rendering on the desktop

Server-rendered, indexable pages

Live updates without client code

Hot reload on web and desktop

Platforms and roadmap

Today and next

The same pages on every target Aioros supports, and the ones it is growing into.

Web

Available

Windows

Available

macOS

Available

Linux

Available

Android

iOS

Preview: web, Windows, macOS and Linux

Design time for people and agents

Android and iOS

Version 1.0

FAQ

Questions, answered

Do I write any JavaScript?

No. Pages are XAML and C#. The framework ships a small script for navigation, live updates and motion, and every page works without it.

How does a XAML page become HTML?

Each page is traced once into a plan that writes its HTML and CSS straight from the view models, so a request does almost no work.

Can I bring my existing XAML?

Yes. Aioros speaks the XAML of Avalonia, with its controls, styles, bindings and view models.

Is it ready for production?

It is a preview: the framework and its libraries are tested and measured, and their APIs may still change before 1.0.

What does it run on?

.NET 10 on the server and the desktop: any browser on the web, and native windows on Windows, macOS and Linux.

Get started

Build your next app in XAML

A template with a real dashboard, a dev server with hot reload, and one codebase for the web and the desktop.

Get started Open the gallery

bash

dotnet new install Aioros.Cosmo.Templates

dotnet new cosmo -n MyApp

cd MyApp && aioros dev

✓ Ready on http://localhost:3000 · hot reload on

Install the templates

dotnet new install Aioros.Cosmo.Templates

Create an app

dotnet new cosmo -n MyApp

Run it with hot reload

cd MyApp && aioros dev

Add --desktop to open the same app as a native window.