Welcome to cratera — the program that lets you run code safely and instantly. If you've ever used an online coding judge, an AI sandbox, or a platform that runs code from the internet, you've needed what cratera does best: run untrusted code without fear. And all of this happens in less than 5 milliseconds.
Imagine this: You want to test a piece of code from a stranger. You don't know if it will crash, steal data, or do something harmful. With cratera, you don't need to worry. You can run anything, and cratera's special technology keeps your computer safe and sound. It's like a digital blast-proof bunker for code.
At its core, cratera is a "microVM execution engine". Don't worry about the fancy words. What it means is: cratera creates a tiny, isolated "bubble" on your computer. Inside this bubble, programs can run freely. If a program crashes, tries to spam your network, or contains a virus — the bubble contains it all. Nothing gets in or out without your permission.
Programs start in under 5 milliseconds (that's 5 thousandths of a second). It's like snapping your fingers.
Using "Zero-NIC network isolation," cratera cuts off network access completely to each code session unless you explicitly allow it.
Python, JavaScript, Java, C++, Rust, Go, and more. Whatever code you have, cratera is ready to run it. No downloads, no installs.
cratera is built for online judges (like coding challenge websites), AI sandboxes (where you let an AI run code), or any developer who needs to run code from other people safely. But you don't need to be a server developer to get value. Here are everyday uses:
We'll have you running in just a few minutes. Follow these steps carefully — it's easier than you think. No programming knowledge needed. We've made it as simple as clicking and running.
.zip — for Windows users, we provide an easy package (it might say "win64" or just "windows" in the name). Click the download link that ends with .zip.
Win + E and clicking "Downloads." You'll see a file called something like cratera-windows.zip.
cratera.exe (it might have the cratera logo next to its name). Double-click it. That's it — cratera starts immediately. The program will show you a simple screen where you can paste code, choose a language, and click "Run."
💡 Windows SmartScreen Notice: When you first run cratera.exe, Windows might show a blue popup saying "Windows protected your PC." This is a defensive measure. Click "More info" and then "Run anyway." This is safe because you downloaded the official file from the source above.
Once cratera is open, let's make sure it works. Here's a simple test:
print("Hello, cratera!")Hello, cratera!That's it! You're officially a cratera user. You can now paste ANY code (JavaScript, C++, Java, you name it) from anyone, and run it safely. If it's bad code, your computer is fully protected.
You don't *need* to know this, but it's nice to understand why cratera is so special:
Export your code sessions to share with others in an encrypted format. Perfect for