Wiktionary
fact is
adv. (context idiomatic sports English) actually, in truth
Usage examples of "fact is".
Tom may have taken the moral high ground, acting from his lofty-sounding principles, but the fact is he left you with nothing and this is your payback.
Miss Monahan will be putting herself in danger if she tries to help me directly now, and& the fact is I would much rather that she not.
The fact is, some neon lights and a few one-stop wedding chapels would make Von Braunville look an awful lot like that down-on-its-luck Nevada city.
I dont know how many hundreds, or perhaps thousands, of jokes Ive told at one time or another in my life, yet the fact is I never made up one.