WSL

A computer always runs an operating system: the program that manages files, draws windows, and launches other programs. The best-known ones are Windows, macOS, and Linux. Linux is a free operating system that powers almost all servers on the internet. Programs are usually built for just one operating system and don’t run elsewhere. WSL solves this problem in one particular direction: it is a built-in feature of Windows that lets Linux programs run directly under Windows. The abbreviation stands for “Windows Subsystem for Linux.”

Why developers need two worlds at once

Most people work at their desk with Windows. But software is mostly written for Linux servers. Anyone programming a website or an AI application will ideally want to test it in exactly the environment it will later run in. Otherwise the program works on their own machine but fails in production.

In the past there were two inconvenient ways to do this. You could set up the computer to boot either Windows or Linux, and had to restart every time. Or you could run an entire second system in a window, which consumed a lot of memory and was sluggish. Both meant constantly switching between two separate workspaces.

WSL makes this switching unnecessary. You open a window, type Linux commands, and keep working with your familiar Windows programs at the same time. Files can be shared between both sides. For many companies, this was the reason to let their developers keep using Windows laptops instead of switching to Macs or Linux machines.

A real Linux kernel in Windows' basement

The heart of every operating system is the kernel. It allocates processing time, manages memory, and talks to the hardware. Programs send requests to this kernel, such as: “open this file.” Linux programs phrase these requests in a language the Windows kernel doesn’t understand.

The first version of WSL tried to translate every Linux request into a matching Windows request. This often worked, but not always, and was slow for file access. Since WSL 2, Microsoft has taken a different approach: a real Linux kernel runs alongside, one that Microsoft itself maintains and ships. It sits inside a very lightweight virtual machine—that is, a simulated computer within the computer.

The difference from a classic virtual machine lies in how it’s used. The Linux system has no screen of its own and no separate start button you’d have to press first. It starts up in a fraction of a second in the background as soon as you need it, and shares networking and files with Windows. To the user, it feels like an additional command line; technically, it’s a second operating system.

WSL in AI projects and in practice

WSL is especially visible in the world of artificial intelligence. Almost all tools for training and running AI models are developed for Linux first. Tutorials online therefore naturally assume Linux commands. Anyone wanting to follow along on Windows opens WSL and can copy them line by line.

Access to the graphics card matters here. Modern AI models don’t compute on the main processor but on specialized graphics chips. WSL 2 can pass these chips through, so that a model running in the Linux environment can use the full performance of the Windows hardware. This is exactly what has made WSL appealing to students and beginners who don’t have their own server.

You’ll mainly encounter this term in installation guides, in forums, and in job postings for software development. A common misconception is that WSL is Microsoft’s own Linux distribution. It’s only the foundation: which Linux variant you install on top of it, such as Ubuntu or Debian, is up to you, and you can even run several side by side.