how to tell?

[haha^36]

I'm planning on transferring my pokemon to gen 6, but how exactly can someone tell which of the pokemon is hacked?

[Porygon-ZZZ]

Pokémon Transfer won't let them through even if they are hacked, so in other words all your hacks won't get through.

[LinuxUser]

Poketransfer will tell you something is wrong with the pokemon and it will stay on your game. Its not the best i tried to transfer hacks iv gotten over the gts and most make it though but it does stop really bad hacks like the ones that said found on route 1 lv 100...

[TheManyFacesOfGlalie]

It basically only filters hacks that were impossible to get legitimately. If it is a Legal Hack, it will go through, and Illegal Hacks won't.

The only ways to tell for sure is to remember which ones you hacked, or to use Pokecheck before transferring.