Use draftCompile flag: Enable faster, but less-optimized, compilations. draft compile only for gecko: -Dgwt.userAgent=gecko1_8 -Dgwt.draftCompile=true, Total time: 2:10.928s (3:05s without it) Saves a cool one minute (more time to be stuck in traffic) *obviously gwt developers should test their code fully compiled (for all browsers and without drafCompile flag) Thanks, Gilad.