HappyPack

HappyPack accelerates webpack builds by parallelizing file transformations across multiple Node.js worker threads. Version 5.0.1 (last release) is in maintenance mode; the author recommends webpack 4+'s built-in thread-loader for new projects. Key differentiator: it was the first widely-adopted parallel loader for webpack 1-3, but it has limited support for certain webpack loader APIs and is not actively developed. It remains useful for legacy webpack setups where migration to thread-loader is not feasible.