e5 probably.
What is the best response to 1.c4?

on my point of view, its 1...d6! because this move falls within my comfort zone. Aside from the Petroff defense, against all white's first move, I usually reply with 1...d6.


I like to play 1...e5 and try to get a reversed Closed Sicilian that the computer calls the Kings English for some reason.


As an English player, I most like to see 1. e5 as a response. 1. c5 doesn't really bother me much either. I least like facing either the Anglo-Dutch (1. c4 f5) and especially someone who really knows how to play an Indian setup (1. c4 Nf6), but that is at least partially because I have the least experience facing those.
What do you play against 1. d4? In many cases, you would be better off playing whatever that is, since it will often transpose with an eventual d4 push by white anyway.

I play 1...e6 and 2...d5 trying to get into a QGD. White's other options aren't that dangerous.
I feel 1...e5 is the most principled, making use of White's flank opening by placing a pawn in the center. Principled does not mean good or fit for you though :-)
1...c5 is also fine (can lead to variations where the symmetry is kept for a very long time), 1...Nf6 as well of course.
Best way is to keep things flexible
start with 1.. NF6 , then e6 for instance.
responding with other options is not bad, but commits you straight to an opening. forinstace english symmetrical or dutch or slav .
I play a lot of english, most of the time with g3 Bg3 or if black goes e5 then e4 to get a kight on d5
there may not be a best response , becasue the move you make probably fits your play style. getting into a symmetrical english may be or not be your cup of tea.
keep things flexible, or, if you master certain response , go for those
What is the best response to 1.c4?
Is it 1.c5,1.d5,1.e4,1.Nf6 or else ?