See the alpha release notes for the 0.20 major release details - https://github.com/systemjs/systemjs/releases/tag/0.20.0-alpha.1.
Features
- Separate optimized 5KB SystemJS production build for just loading System.register modules with baseURL, paths, map, contextual map, bundles, depCache and wasm support.
- depCache now uses link preloading instead of partial execution techniques which have been unreliable.
Breaking Changes
- Removes support for the
load
plugins introduced in the 0.20 alpha.