Currently, the SW script generated by @angular/service-worker is unminified. This was intentional so that it was easier to debug and the stack traces (that people having issues might provide) would be easier to interpret. This is not a major concern, since the SW scripts are aggressively cached by the browser and downloaded/parsed/executed out-of-band with page rendering.

Nonetheless, now that the SW is more stable, it may make sense to minify it for production (with sourcemaps for debugging).

(Related/Duplicate issue: angular/angular-cli#11538)