Windows Subsystem for Linux is a compatibility layer that enables you to install and run Linux distributions (Ubuntu, Debian, Fedora) directly on Windows. Unlike virtual machines, WSL integrates Linux at the OS level, giving you direct access to Linux binaries and file systems without the resource overhead of full virtualisation.
WSL comes in two versions. WSL1 uses translation to convert Linux system calls to Windows equivalents, which works well for most development tasks but can be slower with file operations. WSL2, available on Windows 10 version 2004 and later, runs a lightweight Linux kernel inside Hyper-V, offering better performance and full system call compatibility.
Why developers use it: You get access to Linux package managers (apt, yum), development tools (gcc, Python, Node.js), and bash scripting without leaving Windows. Your file systems are separate though: Linux files live in a virtual disk, and accessing Windows files from Linux is slower than native access.
Common gotchas: File system performance differs between WSL1 and WSL2. Some users experience slower performance when accessing Windows drives from WSL2. You'll need virtualisation enabled in your BIOS. Not all graphical Linux applications work without extra configuration (WSLg adds limited GUI support on newer versions).
WSL is particularly useful for web developers, system administrators, and anyone who needs Linux tools but primarily works in Windows. It's free and installed through the Microsoft Store or command line.