good one, really instuctive thanks
Beat the King's Gambit as Black!

I am pretty sure you will hardly see King gambit in top GM level anymore >2700+.
It is already known that black get significant advantage in King gambit.
One of the worst opening for white. (another worst opening is 1. g4)

Flakbeer countergambit :
Here with e5xf4, black transposes into modern defence :
This move order (d5 before e5xf4), is used to avoid Bc4 line (and others) after 1.e4 e5 2.exf4 Bc4, because after 1.e4 e5 2.f4 d5 3.exd5 exf4 4.Bc4 Qh4 gets a superior version of bishop king's gambit for black.
The variations given in this video are effetive for black, this is the way Lysyj and Ovetchkin advocate in their very good work "The open game for black".

Bobby Fischer knew the Falkbeer Countergambit yet didn't choose it when he wrote his famous The King's Gambit is Busted article in Chess Life after Spassky beat him with it in the early 60's.
Still, thanks for the insights - it worth trying against non-masters.

well, this "side line", is the main way to play against king's gambit at top level since a decade and more.
Accepting the pawn and keeping it with g5 doesn't refute the king's gambit : black here just play a "simple" position, or let's say a practical line.

I play the King's Gambit pretty frequently and I have never seen this. I would consider trying to hold onto the d5 pawn with c4 and then a quick d4 setting up a central pawn wedge instead of ceding the bishop pair for nothing.

I am pretty sure you will hardly see King gambit in top GM level anymore >2700+.
It is already known that black get significant advantage in King gambit.
Sad, but unfortunately true.
Actually, it's not true. White is fine in the King's Gambit. The trouble is that Black is also fine, and more easily fine. whereas White often has to work to be fine. That's not really a scenario a top GM wants with the white pieces. Especially when Black has numerous ways of being fine.
Dear chess community, today I would like to give you my recommendation when facing king's gambit as black. I teach a solid line which promises black a little better position without the need of memorizing lots of theory. Instead of going after the sharp lines, you will get to a solid position where white failed to create a mess on the board (I believe that's the reason why they play king's gambit afterall).
Link to the video: https://youtu.be/cIt5sdduH2E