De or het feitcode?

The correct Dutch article is:

de feitcode

Rule Words ending in -ode: always de. See the rule

How to use feitcode

the feitcodede feitcode
this feitcodedeze feitcode
that feitcodedie feitcode
our feitcodeonze feitcode
your feitcodejouw feitcode
every feitcodeelke feitcode
which feitcode?welke feitcode?
a big feitcode / the big feitcodeeen grote feitcode, de grote feitcode