Build once. Ship one file.

No installer. No per-OS port. No signing dance. A Krate app is tens of kilobytes, runs on Mac, Windows and Linux from the same file, and cannot touch anything it did not declare.

macOS -- universal Windows -- x64 Linux -- x86_64

All downloads →

Source

Someone sent you a file? Here's how it opens.

Krate Studio building a habit tracker from one sentence

All true today -- Krate 0.2.5, August 2026

Your AI already knows how.

Krate Studio works with the AI you already pay for -- Claude, ChatGPT, Grok or Gemini -- and teaches it to build real apps for your computer. Your sign-ins stay on your machine; Krate never sees them. What comes out is a real app you can keep, use, and send.

Works with your AI

Plain words in

A real app out

Write it. Pack it. Ship it.

Your code, your toolchain, your editor. One file out the other end, and no platform between you and the person using it.

Write it

Rust today, compiled to WebAssembly. Bring an app you already have with krate port, start from a template, or let an AI draft it and take over from there.

Pack it

One command produces one .krate: your app, its manifest, and the source that made it. Tens of kilobytes, and the same bytes on every platform -- there is no per-OS build.

Ship it

Send the file, a link, or a card. Your user needs the player once -- free and open source -- and every app after that just opens. No installer for you to maintain, no certificate per platform.

The numbers, and how to check them.

Every figure here came from a command you can run yourself. Where the honest answer is "not yet", it says that instead.

Size

measured

13 KB

A playable 2D game -- paddle, bricks, lives, a win state
A markdown viewer, ported from 4,863 lines: 51 KB
An image viewer, ported from 2,677 lines: 77 KB
Ten complete apps together: 283 KB

Against Electron apps, which ship a browser in every copy: Discord is 431 MB, VS Code 1.4 GB. ls -la evidence/ported/*.krate

Portability

six targets

1 file

Intel and ARM, for each of Mac, Windows and Linux
The same bytes on all of them -- there is no per-OS build
Nine apps re-run nightly on all three, and the output is checked
Your user installs the player once, then files just open

ARM Windows is included because a Windows VM on an Apple Silicon Mac is ARM -- which is how most people try Windows.

The wall

enforced

0 trust

An app reaches nothing it did not declare in its manifest
The runtime enforces it, whatever the code says
The person sees the list before the first line runs
956 tests, and a fuzzer on the bundle parser

Read what any app asks for without running it: krate run app.krate --dump-caps

What we do not claim: a cold-start number. Most of a start is window and GPU setup that any app pays, and we have not instrumented time-to-first-frame yet -- so we do not print one.

Free while we build it.

Everything here is free, with no cap and no meter. We will charge one day, and we will say so long before we do -- but nobody should bet their distribution on a runtime that might price them out at app four.

The player

open source

MIT and Apache licensed
Runs any .krate on Mac, Windows and Linux
Every capability an app asks for is enforced by the runtime
Build it from source if you would rather

Read the source

Everything else

free, for now

Make as many apps as you want
Ship them as a file, a link, or a card
Your toolchain, your code, your AI -- or ours
Every app you make is a file that is yours forever

Someone sent you a .krate? Opening apps is free, forever -- here is how.

Ready to ship
without the port?

Free, no cap. Build once, get one file, and send it to anyone on any desktop -- no installer, no per-OS build, no signing dance.