Yarn Classic Package Manager

Yarn Classic is a fast, reliable, and secure dependency management tool for JavaScript and Node.js projects, currently at stable version 1.22.22 and supporting Node.js versions 4.8.0 and above. Released under the BSD license, it caches every downloaded package locally so that subsequent installs never require re-downloading, and it parallelizes network operations to maximize resource utilization and dramatically reduce install times compared to npm. Security is enforced through checksum verification of every installed package before its code executes, preventing supply chain tampering. The deterministic lockfile format combined with a precise install algorithm guarantees that any installation that succeeds on one machine will produce identical results on every other machine, regardless of install order or timing. Additional capabilities include full offline installation of previously cached packages, efficient network request queuing that avoids request waterfalls for optimal throughput, network resilience that automatically retries failed requests, and a flat mode for simplified dependency trees. The tool installs any package from the npm registry while maintaining full compatibility with existing package workflows. Note that this documentation covers Yarn 1, which is in maintenance mode, while Yarn 2 and above (known as Yarn Berry) represents the actively developed modern version with additional features. The tool was originally created by Sebastian McKenzie in 2016 and quickly became an industry standard adopted by major companies including Facebook, Google, and Microsoft.