Proper File Format Genesis

[Rodimus Primal]

I know GoodGen uses .MD as a proper file format but I was wondering, what is the true Genesis file format? .NES is accepted as Nintendo, .SFC for Super NES, etc but Genesis has .gen, .md, .bin(which I don't care for because of file association), .smd, and then some others.

[WitchHunter]

When you dump a cardridge you copy the data from the cardridge roms banks to a binary file.
BIN is the correct extensions, but you can use any extension you want (most emulators read the file as BIN).

In USA the consolle was named Sega Genesis. Sega Megadrive in Japan and Europe.

You can use the GEN extension USA dumps.

[Ragnar]

When you dump a cardridge you copy the data from the cardridge roms banks to a binary file.
BIN is the correct extensions, but you can use any extension you want (most emulators read the file as BIN).

BIN isn't necessarily a correct extension. Certainly some (not all) copiers appended the roms with that extension. The only way to tell a games correct extension is to check the header appended on by the dumping copier and see whatever it wanted. But that's pointless, as old copier headers are entirely unneeded, as are the extensions they tried to establish. Most likely 99% of the roms floating around the net feature incorrect extensions nowadays

GEN makes the most common sense at a glance. I'd lean towards SMD though as it has a nice dual meaning. Sega Megadrive would be the obvious meaning, but IIRC the Super Magic Drive dumped to SMD files

[Rodimus Primal]

From what I've gathered, SMD is Super Magic Drive. GEN files are usually renamed BIN files and MD is what GoodTools uses.