hahaha, i totally agree - if it is 50x larger i would use a different tool too :) But as i said, if your source is 100KB it's not 50x larger, maybe it's 20% larger than hand written JS. Currently the footprint of the js-code is around 150KB. While dart2js is evolving this number is declining constantly. In the end when you add js-minification you will have a footprint of maybe 20-30KB i guess.