@konsoletyper In my first project, whenever I change a .kt file - the generated js file is updated right away... in my second project, I must rebuild (or I guess build) to get the code updated in the browser.. I just had a thought though... the 1st project it is the kotlin code. The 2nd project I was testing javascript code in the index.html even though it is also a kotlin js project... so I think I understand better how things works. If it is kotlin, no need to build. If it is other files in the project, must build