What chess position has the most number of possible moves?

And here is another legal position before any promotions are made, this time with 142 moves for White:

If it's black to play, there is 0 moves...

A very interesting waste of time!

:tup

rrrttt posted on Feb 6 2010 a position with 216 possible moves, but claimed that this yields 218 moves. However, there is a position with 218 moves. Actually one gets a position with 218 moves by moving the white King in rrrttt's position one place to the right, i.e from e1 to f1. See also https://www.chessprogramming.org/Chess#Chess_Maxima This also answers the Question of HarshHose, which also has been answered by RandJoe.

However I still don't know any proof that more than 218 is not possible. Thus we only have a position of 218 moves as a lower bound for the maximum number of moves possible in a legal chess position. I have a proof that more than 268 is not possible.
This upper bound is lousy in the sense, that it is based on wildly unrealistic optimistic assumptions. I have some ideas to improve this upper bound substantially. My feeling is that 218 is very close to the maximum, if it is not already the maximum.

I came up with this position that has 270 legal moves:

Can you do better than this?

This may jeopardize some compression algorithms for chess games that use 8 bits for the maximum number of legal moves.

Does this position actually have 218 legal moves? I used a program to generate all the legal moves for white and there are only 216.

I could only find 265 legal moves: Qa1b2, Qa1c3, Qa1d4, Qa1e5, Qa1f6, Qag7, Qbb2, Qbb3, Qbb4, Qbb5, Qbb6, Qbb7#, Qbc2, Qbd3, Qbe4#, Qbf5, Qbg6, Qc1c2, Qc1c3, Qc1c4, Qc1c5, Q1c6#, Q1c7, Qcb2, Qcd2, Qce3, Qcf4, Qcg5, Qd1d2, Qd1d3, Qd1d4, Q1d5#, Q1d6, Q1d7, Qdc2, Qdb3, Qde2, Qdf3#, Qdg4, Qe1e2, Qe1e3, Qe1e4#, Qe1e5, Q1e6, Q1e7, Qed2, Qec3, Qeb4, Qef2, Qeg3, Qf1f2, Qf1f3#, Qf1f4, Qf1f5, Qf1f6, Q1f7, Qfe2, Qfd3, Qfc4, Qfb5, Qfg2#, Qg1g2#, Qg1g3, Qg1g4, Qg1g5, Qg1g6, Qg1g7, Qgf2, Qge3, Qgd4, Qgc5, Qgb6, Kg2, Qa2b2, Qa2c2, Qa2d2, Qa2e2, Qaf2, Qag2#, Q2b3, Q2c4, Q2d5#, Q2e6, Qaf7, Qh2g2#, Qh2f2, Qh2e2, Qh2d2, Qh2c2, Qh2b2, Q2g3, Q2f4, Q2e5, Q2d6, Q2c7, Qa3b3, Qa3c3, Qa3d3, Qae3, Qaf3#, Qag3, Q3b2, Q3b4, Q3c5, Q3d6, Qae7, Qh3g3, Qh3f3#, Qh3e3, Qh3d3, Qh3c3, Qhb3, Q3g4, Q3f5, Q3e6, Q3d7, Q3g2#, Qa4b4, Qa4c4, Qa4d4, Qae4#, Qaf4, Qag4, Q4b3, Q4c2, Q4b5, Q4c6#, Qad7, Qh4g4, Qh4f4, Qh4e4#, Qh4d4, Qhc4, Qhb4, Q4g5, Q4f6, Q4e7, Q4g3, Q4f2, Qa5b5, Qa5c5, Qa5d5#, Qa5e5, Qaf5, Qag5, Q5b4, Q5c3, Q5d2, Q5b6, Qac7, Qh5g5, Qh5f5, Qh5e5, Qhd5#, Qhc5, Qhb5, Q5g6, Q5f7, Q5g4, Q5f3#, Q5e2, Qa6b6, Qa6c6#, Qa6d6, Qa6e6, Qa6f6, Qag6, Q6b5, Q6c4, Q6d3, Q6e2, Qab7#, Qh6g6, Qh6f6, Qh6e6, Qh6d6, Qhc6#, Qhb6, Q6g7, Q6g5, Q6f4, Q6e3, Q6d2, Bb6#, Bc5#, Bd4#, Be3#, Bf2#, Q7g7, Q7f7, Q7e7, Q7d7, Q7c7, Qhb7#, Q7g6, Q7f5, Q7e4#, Q7d3, Q7c2, Bc7#, Bd6#, Be5#, Bf4#, Bg3#, Qc8c7, Qc8c6#, Qc8c5, Qc8c4, Qc8c3, Q8c2, Qcd7, Qce6, Qcf5, Qcg4, Qcb7#, Qd8d7, Qd8d6, Qd8d5#, Qd8d4, Q8d3, Q8d2, Qde7, Qdf6, Qdg5, Qdc7, Qdb6, Qe8e7, Qe8e6, Qe8e5, Q8e4#, Q8e3, Q8e2, Qef7, Qeg6, Qed7, Qec6#, Qeb5, Qf8f7, Qf8f6, Qf8f5, Q8f4, Q8f3#, Q8f2, Qfg7, Qfe7, Qfd6, Qfc5, Qfb4, Qg8g7, Qg8g6, Qg8g5, Qg8g4, Q8g3, Q8g2#, Qgf7, Qge6, Qgd5#, Qgc4, Qgb3, Qh8g7, Qh8f6, Qh8e5, Qh8d4, Qh8c3, Q8b2

Is there something I'm missing?

No, sorry man, diagonals B6-F2 and C7-B3 are controlled only by one queen. Therfore there are 265 moves in that position.

The last two positions with tons of queens had no way for Black to have made the last move, so Black was on move and they were stalemate.