edit: i like the suggestion at the bottom of the thread
the most, scroll down for some tl;dr conclusions
greetings and salutations
there are a couple ways i think this useful feature could be implemented. in both cases, it would work just like the size checker that stops you from uploading a file that's too large for the format you're uploading to. sorry n00b! this format is .nsf only!
in which the vast majority of formats are restricted to only the allowed filetypes shown on their lyceum article. uploading any other file type will give you the dialog box that stops you + tells you why. there are a few formats where this gets complicated, such as adlib and gameboy; and i would suggest not implementing it for wildchip/fakebit(/allgear?) since they can receive hardware-specific files in majors.
that's the more heavy-handed option, and notably could require a bit of work from time to time if filetypes are added, restrictions change, etc.
in which the only thing that gets checked for is .mp3/.wav/.flac/.ogg files being submitted to all the formats that require something else. the checker stops you & gives you a dialog box telling you what the valid filetypes are, and to read the lyceum article for more info.
that option is a bit more kind and still prevents the most common version of this feel-bad situation, but it doesn't stop things like "people submitting .ftm to nsf-formats" for example (which i think is the 2nd most common lol).
i'm suggesting this feature because i've seen it happen a lot! the site's a bit overwhelming for new folks and i think it's easy to misunderstand what's allowed and what isn't. having a checker in place would both save them from stepping headfirst into not following format rules, and save us from needing to point that fact out after they already submitted. i always worry that this could be a contributing factor in people bouncing off the site early if this situation happens.