In the context of downloading something from the Internet, e.g. Films, there are at least the three different verbs. What could be the difference between them?
I once used downloaden in my writing homework, but then my teacher corrected it with runterladen. However, the original verb was not struck out, meaning it is not totally wrong. When searching for the meaning of "runterladen", I also got herunterladen.
Reasonably, downloaden may be derived from the similar english verb "download".
The linguee dictionary is not much helpful: