Mesen was previously banned due to what was believed to be an undetectable feature (ie: run-ahead lag reduction) that could yield an unfair advantage from a speedrunning perspective. A fairly simple detection method for run-ahead was brought to my attention, and I find that it's easy enough to warrant allowing Mesen back.

So from now on, Mesen is no longer banned. However, showing the input display will be MANDATORY. Mesen runs without the input display being shown will not be accepted.

NEWS: While we will certainly keep supporting Mesen within the same conditions that were previously underlined, I would like to direct players to the following:

https://github.com/threecreepio/mesenrta/releases

This is a Mesen release compiled by threecreepio for the SMB1 community. It basically strips the run-ahead feature and shows the input display by default on screen. I would definitely recommend speedrunners using Mesen to move to this fork of Mesen as I'm sure more and more games will follow in SMB1's initiative and allow this fork.