I would have voted front end but then I remembered that I intentionally avoid any work that needs to support old browsers because they are so much of a pain in

I would have voted front end but then I remembered that I intentionally avoid any work that needs to support old browsers because they are so much of a pain in the ass. So in the end I would say it's a mix of both. Front end is fun because I actually get to build what user will use and back end is fun because I get to make the plans or extensive stuff that will decide how efficient the code is and how much flexible / future proof it can be. OP can you add an option of "both".