What if white doesn't play 2.c4?

After 1.d4, the mainline is 2.c4. However, many lower leveled players avoid this move and tend to play moves like 2.e3 and 2.Nf3. I don't spend much time studying openings and as such, I don't really have a solid reply for moves such as these. Does anyone have any suggestions as to how I can meat these offbeat white systems and if white can reasonably expect better than equality? I especially need help against the London system with 2.Bf4.

What do you play after 1.d4? Nf6 or d5?

I normally play 1...Nf6.

Try to get in ...c5 yourself, and eye solid development.

Many times a KID set up will work well against an offbeat d4 opening.

You will find that most of the time 2.Nf3 and to a lesser degree 2.e3 will transpose to one of the main lines. Ofcourse if white wants to avoid popular openings can deviate with 2.e3, 3.c3 or 2.Bg5,3.e3 etc etc. However most of the time when white follows this road black will be left in peace to develop any way he wants.

2. Nf3 or 2. e3 are not off-beat moves for white.

Instead of memorizing lines of book openings, ask yourself why those moves are being played. For example, why does white play 2. c4?

I love to play Bf5 whenever possible, getting rid of my greatest weakness (my bishop).  But the line isn't popular at the highest levels for some reason unknown to me, and if you don't know what you are doing, or you play it at an inappropriate time, Qb3 kills.

Well, when I mention moves like 2.e3 and Nf3, they normally don't follow it up with c4 at all. I know that white's main try for an advantage is with 2.c4 so I just wanted to know the best plan to take advantage of white not making the "strongest" move available.

What opening do you play as Black versus 1. d4 Nf6 2. c4?

It's all very well for people to suggest a King's Indian setup but if you don't actually play the KID you will have a problem when someone plays c4 a move or two late.

Also the Trompowsky Attack (2. Bg5) is a separate opening. You have to learn something specific against it.

I actually don't have a defense I use 100% of the time against 2.c4. I either use the Benoni, the Grunfeld or occassionally attempt a Nimzo-Indian. I tend to avoid the King's Indian unless I don't feel like playing one of the other systems.

Benoni-type lines work well against offbeat d4 openings.  You should get a solid enough position from just logical moves.  Also, pay close attention to which moves your opponent is playing.  2.  e3 shouldn't be a real threat to your Benoni structure, but 2.  Nf3 can still lead to Benoni mainlines.

Whenever I play 1.d4 Nf6 2.Nf3, it's usually as a useful waiting move which avoids the Benoni and Benko. [And Budapest, though not sure why you'd want to avoid that].

2021: What if White plays 2.c4 ?!?!

Against the London, you’re better off with studied anti-lines. For example a good counter could be 1.d4 d5, 2.Bf4 Nf6, 3.e3 e6, and then whatever white plays you’d usually play Bd6 to trade the dark-squared bishop. If they move it back one square you don’t trade it. There are other scenarios, but you only trade if they take you, or after they castle. Fight for the center is important, and your move five should be something like c5 to pressure white’s center. There’s a free course on chessable called short and sweet QGD that is playing as black going for the QGD line against the QG. He covers a counter against the London.