Please have a look at move 42 (black) on the following Computer Analysis: http://www.chess.com/home/computer_analysis?id=57954312&game_type=1. There move "f3" is stated to be a mistake, and at the same time, it is proposed as the best move. There must be something very fishy there.

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Apparently, we can't do this. You'd have to cut and paste the game score and analysis into the forum.

Very well then: This is the link to the game http://www.chess.com/echess/game?id=57954312 (this should work - I've checked it). Following is the analysis as output by the Computer-Analysis tool with a strength of 2500 (it says). As already stated in the opening post, it marks move "42 Bd4 f3?" with a question mark and proposes in its alternative exactly the same move. 1. f4 c5 2. e3 Nc6 3. Nf3 g6?! ( 3... Nf6 4. Bb5 e6 5. O-O Be7 6. Nc3 O-O 7. Ne5 Qc7 8. d4 a6 9. Nxc6 dxc6 10. Be2 Bd7 ) ( 3... g6 4. Be2 Nf6 5. O-O Bg7 6. c4 O-O 7. Nc3 d5 8. cxd5 Nxd5 ) 4. d4 b6? ( 4... cxd4 5. exd4 Nf6 6. Nc3 Bg7 7. Bb5 a6 8. Bxc6 dxc6 9. O-O O-O 10. Ne5 Be6 11. Be3 ) ( 4... b6 5. d5 Na5 6. Be2 Bg7 7. O-O Nf6 8. Nc3 d6 9. e4 O-O 10. Bd2 e6 11. dxe6 Bxe6 12. Ng5 ) 5. c3 e6?! ( 5... Nf6 6. d5 Na5 7. Be2 Bg7 8. O-O O-O 9. c4 Ba6 10. Qc2 d6 11. e4 Qc7 12. Rd1 ) ( 5... e6 6. Bd3 Bb7 7. O-O d5 8. Nbd2 c4 9. Be2 Nf6 10. Ne5 Qc7 11. e4 Nxe4 ) 6. Bd3 Bb7?! ( 6... Bg7 7. O-O Nge7 8. dxc5 bxc5 9. e4 d5 10. Be3 c4 11. Bc2 O-O 12. Na3 Rb8 13. Qc1 Ba6 14. Rd1 Qa5 15. Ng5 Rfd8 16. Rd2 ) ( 6... Bb7 7. O-O d5 8. Nbd2 Nf6 9. Ne5 Qc7 10. Bb5 a6 11. Be2 O-O-O 12. Nxc6 Qxc6 ) 7. O-O f5?! ( 7... d5 8. Nbd2 Nge7 9. Qa4 Bg7 10. Qa3 cxd4 11. exd4 O-O 12. Ne5 Nf5 13. Ndf3 ) ( 7... f5 8. c4 Nf6 9. Nc3 Be7 10. d5 exd5 11. Nxd5 O-O 12. Bd2 Nxd5 13. cxd5 ) 8. Ne5 Nh6?! ( 8... Bg7 9. Nd2 Nge7 10. Ndf3 O-O 11. Nxc6 Bxc6 12. Qc2 Nd5 13. Bd2 d6 14. c4 Nb4 15. Bxb4 cxb4 ) ( 8... Nh6 9. Nd2 Be7 10. Ndf3 Nxe5 11. fxe5 O-O 12. Bd2 Nf7 13. Qb3 Qc7 14. Qa4 ) 9. Nd2 d6 10. Nec4 Ba6?? ( 10... Be7 11. Nf3 O-O 12. Be2 b5 13. Qb3 Ba6 14. Nce5 Nxe5 15. fxe5 c4 16. Qd1 Nf7 17. exd6 Nxd6 18. d5 ) ( 10... Ba6 11. Nxd6+ Bxd6 12. Bxa6 Qd7 13. Nc4 Nf7 14. Bb5 cxd4 15. Qa4 Rc8 16. exd4 O-O ) 11. Qe2?? ( 11. Nxd6+ Bxd6 12. Bxa6 Qd7 13. Nf3 cxd4 14. exd4 O-O 15. Ne5 Bxe5 16. fxe5 Nf7 17. Be3 g5 18. g3 g4 19. Qb3 ) ( 11. Qe2 b5 12. Qf3 Kd7 13. Na3 c4 14. Be2 d5 15. Qh3 b4 16. Nab1 Qa5 ) 11... d5?! ( 11... b5 12. Qf3 Kd7 13. Na3 c4 14. Be2 d5 15. Qh3 b4 16. Nab1 Qa5 ) ( 11... d5 12. Nd6+ Bxd6 13. Bxa6 Qd7 14. Nf3 O-O 15. Ne5 Bxe5 16. fxe5 Kg7 17. Bd2 Ng4 18. h3 Nh6 ) 12. Nd6+ Qxd6?! ( 12... Bxd6 13. Bxa6 Qd7 14. Nf3 O-O 15. b3 Ng4 16. Bb5 Rae8 17. Bb2 Nf6 18. Ng5 cxd4 19. cxd4 ) ( 12... Qxd6 13. Bxa6 Rb8 14. Nf3 Bg7 15. Bd2 O-O 16. Bb5 Qd7 17. Qd1 Bf6 18. Qa4 ) 13. Bxa6 c4? ( 13... Qc7 14. dxc5 bxc5 15. Qb5 Rb8 16. Qa4 Be7 17. Bb5 Rc8 18. Nf3 O-O 19. Bd2 Ng4 20. h3 Nf6 ) ( 13... c4 14. Nf3 Be7 15. Ne5 O-O 16. Bb7 Rac8 17. Bxc8 Rxc8 18. Bd2 Qc7 19. b3 Nxe5 20. fxe5 Nf7 21. g4 Ng5 22. gxf5 gxf5 ) 14. Bb5? ( 14. Nf3 Qc7 15. b3 cxb3 16. axb3 Bd6 17. c4 O-O 18. cxd5 exd5 19. Bd2 Qe7 20. Qb5 Nb4 21. Ne5 Rfd8 22. Nc6 Nxc6 23. Qxd5+ ) ( 14. Bb5 a6 15. Ba4 Be7 16. Nf3 O-O 17. Bc2 Qc7 18. b3 b5 19. Bd2 Nf7 20. bxc4 ) 14... Be7?! ( 14... a6 15. Ba4 Be7 16. Nf3 O-O 17. Bc2 Qc7 18. b3 b5 19. Bd2 Ng4 20. h3 Nf6 ) ( 14... Be7 15. b3 a6 16. Ba3 Qc7 17. Bxc6+ Qxc6 18. Bxe7 Kxe7 19. bxc4 Ng4 20. h3 Nf6 21. cxd5 exd5 22. c4 ) 15. Bxc6+? ( 15. b3 a6 16. Ba3 Qc7 17. Bxc6+ Qxc6 18. Bxe7 Kxe7 19. bxc4 Ng4 20. h3 Nf6 21. cxd5 exd5 22. c4 Rhc8 23. Rac1 Qe6 24. cxd5 Nxd5 25. Nc4 Qe4 26. Qf2 ) ( 15. Bxc6+ Qxc6 16. Nf3 Nf7 17. b3 O-O 18. Bb2 Rfc8 19. g3 Kg7 20. Kg2 h6 21. h3 a6 ) 15... Qxc6 16. Qf3 Ng4 17. h3 Nf6 18. Rf2 Ne4?! ( 18... Qa4 19. Qe2 Kf7 20. g4 h6 21. Rg2 Bd6 22. Nf3 Rag8 23. a3 fxg4 24. hxg4 Ne4 25. Nd2 Nxd2 26. Bxd2 Qc2 27. Be1 ) ( 18... Ne4 19. Nxe4 fxe4 20. Qd1 Bh4 21. Rf1 h5 22. Bd2 Kf7 23. Kh2 Bf6 24. g3 ) 19. Nxe4 dxe4 20. Qe2 a5 21. a3 a4 22. Bd2 Kd7 23. Raf1? ( 23. Be1 Qb5 24. Rf1 h6 25. Bf2 g5 26. Bg3 Bd6 27. Qh5 Qxb2 28. Qf7+ Kc6 29. Rad1 Qxc3 30. d5+ Kc5 ) ( 23. Raf1 Bh4 24. g3 Bxg3 25. Rg2 Bh4 26. Be1 Bf6 27. Bg3 Rhc8 28. Qe1 Qd6 29. Qd1 b5 30. Qe1 Be7 ) 23... Bh4 24. Kh2? ( 24. g3 Bxg3 25. Rg2 Bh4 26. Be1 Bf6 27. Bg3 Rhc8 28. Qe1 Qd6 29. Bh4 Bxh4 30. Qxh4 Qe7 31. Qh6 ) ( 24. Kh2 Bxf2 25. Qxf2 Qb5 26. Be1 h5 27. g3 Ke7 28. Qe2 Kf7 29. Kg2 Qc6 30. Bf2 ) 24... Bxf2 25. Rxf2 h5 26. Rf1 Kd6?! ( 26... h4 27. Rg1 Rag8 28. g3 hxg3+ 29. Rxg3 Qb5 30. Be1 Ke7 31. Rg1 Kf7 32. Bf2 Rh6 33. h4 ) ( 26... Kd6 27. g3 Ke7 28. Kg2 b5 29. Be1 Kf7 30. Bf2 Qc7 31. Rg1 Rad8 ) 27. Rd1 h4 28. Be1 Rh6?! ( 28... Qc7 29. Qf2 Ke7 30. Kg1 Rad8 31. Qd2 Kf7 32. Bf2 Qe7 33. Rc1 b5 34. Rf1 ) ( 28... Rh6 29. Bf2 Rh7 30. Qe1 Rah8 31. Kg1 Qd7 32. Kf1 Qb5 33. Qe2 Kc7 34. Qc2 ) 29. Qd2 Rg8 30. Bf2 g5 31. fxg5 Rxg5 32. Qe1? ( 32. Qe2 Rg8 33. Rg1 Kd7 34. g4 hxg3+ 35. Bxg3 Rh7 36. Rg2 Rhg7 37. Qf1 Ke8 38. h4 ) ( 32. Qe1 Rhg6 33. Kh1 Rxg2 34. Qe2 R6g5 35. Qf1 Qb5 36. Rb1 Rg8 37. Bxh4 Rxb2 ) 32... Rgh5? ( 32... Rhg6 33. Qf1 Qb5 34. Rd2 Rxg2+ 35. Qxg2 Rxg2+ 36. Kxg2 f4 37. exf4 Qf5 38. Rd1 Qxf4 39. Re1 Kd5 40. Kg1 Qg5+ ) ( 32... Rgh5 33. Qe2 Rh8 34. Kg1 Rg5 35. Rd2 b5 36. Qe1 Rgh5 37. Rd1 R5h7 38. Kf1 ) 33. Rd2 Qc7?! ( 33... Rh7 34. Kh1 Kc7 35. Bg1 Kb7 36. Bh2 Rg5 37. Be5 Rg8 38. Qf1 Qb5 39. Kg1 Rd8 40. Bf6 ) ( 33... Qc7 34. Kh1 b5 35. Bg1 Ke7 36. Bh2 Qd7 37. Be5 Rg6 38. Kg1 Kf7 39. Qf1 Rh7 40. Qf4 ) 34. Kg1 Qd8 35. Qd1 b5 36. Qe1 Qg5 37. Qd1? ( 37. Kh1 Rg6 38. Bg1 Kc6 39. Bh2 Rh8 40. Be5 Rhg8 41. Bf4 Qe7 42. Qf1 Kb6 43. Be5 Kb7 44. Bf4 Rd8 ) ( 37. Qd1 Rg6 38. Qf1 f4 39. exf4 Qxf4 40. Qe1 Qf3 41. Be3 Rf5 42. Kh1 Qf1+ 43. Qxf1 Rxf1+ 44. Kh2 Kd5 45. Bf2 Rh6 ) 37... Rh7? ( 37... Rg6 38. Qf1 f4 39. exf4 Qxf4 40. Qe2 Qf3 41. Be3 Rf5 42. Kh2 Qxe2 43. Rxe2 Kd5 44. Bf2 Rf4 45. Be3 Rf1 46. Bf2 Rh6 47. Be3 ) ( 37... Rh7 38. Kh1 Kc6 39. Bg1 Rd7 40. Re2 Kb7 41. Bh2 Rd8 42. Bf4 Qg7 43. Qf1 Qg6 ) 38. d5 e5 39. Qe1? ( 39. Kh1 R5h6 40. Qe2 Rc7 41. Rd1 Rc5 42. Qd2 Qg8 43. Qe1 Rxd5 44. Bxh4 Rxd1 45. Qxd1+ Ke6 46. Qe1 Rh8 47. g3 Qg7 ) ( 39. Qe1 Rg7 40. Qf1 Rh6 41. Kh1 Rc7 42. Qe2 Rc5 43. Qd1 Qh5 44. Qc1 Rh7 45. Rd1 Qf7 46. Qc2 Rxd5 47. Rc1 Qg6 48. Qe2 ) 39... Rg7 40. Qf1 f4 41. exf4 exf4 *42. Bd4 f3?* ( 42... f3 43. Qf2 Qxg2+ 44. Qxg2 Rxg2+ 45. Rxg2 fxg2 46. Kxg2 Rg5+ 47. Kh2 Kxd5 48. Bf2 Rg6 49. Be3 ) ( 42... f3 43. Qf2 Qxg2+ 44. Qxg2 Rxg2+ 45. Rxg2 fxg2 46. Be3 Kxd5 47. Kxg2 Rf5 48. Bf2 Rf4 49. Be3 ) 43. Qf2 Rg8? ( 43... Qxd2 44. Bc5+ Kd7 45. Qxd2 Rxg2+ 46. Qxg2 fxg2 47. Bf2 Kd6 48. Kxg2 Rxd5 49. Bd4 Rg5+ 50. Kh2 Kd5 51. Bf2 Rg6 52. Be3 Kd6 53. Bf4+ Ke6 54. Bd2 Rg3 55. Bf4 Rf3 56. Bg5 Rf2+ 57. Kg1 Rxb2 58. Bxh4 Kd5 59. Kf1 ) ( 43... Rg8 44. Bc5+ Kd7 45. Qe3 Qxe3+ 46. Bxe3 Rf5 47. Kh2 Kd6 48. Rf2 Kxd5 49. Rd2+ Ke5 50. gxf3 exf3 51. Kh1 Ke4 52. Bf2 ) 44. Bc5+ Kd7 45. Be3?? ( 45. Qe3 Qxe3+ 46. Bxe3 Rf5 47. Kh2 Kd6 48. Rf2 Kxd5 49. Rd2+ Ke5 50. Rf2 Rg3 51. Bb6 Ke6 52. Bd4 ) ( 45. Be3 Qf5 46. Re2 Rxg2+ 47. Qxg2 fxg2 48. Rxg2 Qxh3 49. Bd4 Rxd5 50. Rg7+ Ke6 51. Rg6+ Kf5 52. Rg8 e3 53. Rf8+ Kg4 ) 45... Qf5 46. Qf1?? ( 46. Bg5 Rhxg5 47. Qa7+ Ke8 48. d6 Qd7 49. Qd4 Rxg2+ 50. Rxg2 Rxg2+ 51. Kf1 Qe6 52. Qh8+ Kd7 53. Qb8 Rxb2 54. Qa7+ Kxd6 55. Qb8+ Kc5 56. Qa7+ Qb6 57. Qe7+ Qd6 58. Qa7+ Kc6 59. Qa6+ Kd5 60. Qa8+ Ke5 61. Qh8+ Qf6 62. Qb8+ Kf5 63. Qc8+ ) ( 46. Qf1 Qxh3 47. g3 Qxf1+ 48. Kxf1 hxg3 49. Rg2 fxg2+ 50. Kxg2 Rh2+ 51. Kg1 Kd6 52. Bd4 Kxd5 53. Bb6 Rxb2 54. Be3 Ra2 ) 46... Qxh3 47. Rf2?? ( 47. b4 axb3 48. a4 Rxg2+ 49. Rxg2 Qxg2+ 50. Qxg2 fxg2 51. Bc1 h3 52. Kh2 bxa4 53. d6 Kxd6 54. Bb2 Kd5 55. Bc1 Rf5 56. Ba3 Rf1 57. Kxh3 g1=Q ) ( 47. Rf2 fxg2 48. Rxg2 Rxg2+ 49. Qxg2 Qxe3+ 50. Kh2 Rxd5 51. Qg4+ Kd6 52. Qg6+ Kc5 53. Qg2 Rd2 54. Qxd2 Qxd2+ 55. Kh3 Qxb2 56. Kxh4 ) 47... Qf5? ( 47... Rf5 48. Re2 fxg2 49. Qxf5+ Qxf5 50. Rf2 Qh3 51. Rf7+ Ke8 52. Re7+ Kxe7 53. Bg5+ Rxg5 54. d6+ Kd7 55. Kf2 g1=Q+ 56. Ke2 Qd3# ) ( 47... Qf5 48. Kh1 fxg2+ 49. Qxg2 Rxg2 50. Rxf5 Rxf5 51. Kxg2 Kd6 52. Kh2 Kxd5 53. Kg2 Rf3 54. Bh6 h3+ 55. Kh2 e3 56. Bg5 e2 57. Bd2 Rf1 58. Kxh3 ) 48. Kh2 Qe5+? ( 48... Rg3 49. Rd2 fxg2 50. Qxf5+ Rxf5 51. Bd4 e3 52. Bxe3 Rxe3 53. Kxg2 Rg3+ 54. Kh2 Kd6 55. Re2 Rxd5 56. Kh1 Rgd3 57. Kh2 b4 58. cxb4 Rd2 59. Rxd2 ) ( 48... Qe5+ 49. Kh1 Rg3 50. Qc1 fxg2+ 51. Rxg2 Rxg2 52. Kxg2 Rf5 53. Qe1 Rf3 54. Qxh4 Rxe3 55. Qh7+ Kc8 56. Qg8+ Kb7 57. Qg6 Qxd5 58. Qg7+ Ka8 59. Qf8+ Ka7 60. Qg7+ Qb7 61. Qd4+ Qb6 ) 49. Kh1 Rg3? ( 49... h3 50. gxh3 Qf5 51. Rh2 Rg2 52. h4 Rxh2+ 53. Kxh2 Rxh4+ 54. Kg3 Qh5 55. Bg1 f2 56. Kxf2 Rf4+ 57. Ke1 Rxf1+ 58. Kxf1 Qd1+ 59. Kg2 Qf3+ 60. Kh2 ) ( 49... Rg3 50. d6 Rf5 51. Qe1 fxg2+ 52. Rxg2 Rxg2 53. Kxg2 Qxd6 54. Qxh4 Qg6+ 55. Qg3 Qxg3+ 56. Kxg3 Rf3+ 57. Kg4 Rxe3 58. Kf4 Re1 59. Ke5 e3 60. Ke4 ) 50. gxf3 exf3 51. Rd2?? ( 51. Bd4 Qf5 52. Ba7 Rhg5 53. Bb8 Rg2 54. Rxf3 Rg1+ 55. Kh2 Rxf1 56. Rxf5 Rgxf5 57. Kh3 Rg5 58. Bh2 Rxd5 59. Bb8 Rh1+ 60. Kg2 Rdd1 61. Kf3 h3 62. Kg4 Rd2 63. Bf4 Rxb2 ) ( 51. Rd2 Qxe3 52. Rf2 h3 53. Rh2 Qe4 54. Rf2 h2 55. b4 Rg1+ 56. Qxg1 hxg1=Q+ 57. Kxg1 Qe1+ 58. Rf1 Qg3# ) 51... Qxe3 ( 51... Qxe3 52. Rf2 h3 53. Rh2 Qe4 54. Rf2 h2 55. b4 Rg1+ 56. Qxg1 hxg1=Q+ 57. Kxg1 Qe1+ 58. Rf1 Qg3# )

If you had the PGN, you could convert it into a game, but for now, I am NOT reading that.

Yeah it's nonsense. It said for me 'Black has a decisive advantage' when white was a queen and couple of pawns up.

@Scottrf, I think I see you post something on every single thread on this website.

Yes this is also happened with me. Computer says on my game that 22...fxg4 is a inaccuracy and proposes 22...fxg4 with a small variations and end up that Black has a decisive advantage.

I prefer not to post the link.

chess.com's chess engine is good but not the best. It is useful for convenience and true blunder checks, but if you want a real analysis by a computer, use Fritz or similar. Best is to analyze first without a computer.

I've had chess.com question a move of mine which lead to a mate in 6 or 7 (I got in in 11 or 12 in the game) in favor of a move which didn't lead to mate for another 20 moves or so. Also, chess.com nitpicks about fractions of a point difference in two moves when you are ahead by more than a Queen.

Bottom line is that you should not be surprised by odd analysis when you are using a computer shared by thousands of users. For a few bucks investment in an older version of Fritz, you can get a much better analysis offline.

Chess.com computer is best when it comes to calculating tens of variation in just a single move.

It's just true enough that even though computer is best when it comes to calculations. They're still not good enough on explaining the details of each move.

So I therefore conclude that when it comes to calculation, chess.com engine is better. 

I really appreciate the computer analysis tool and do use it a lot but it is true that if often calls a move an inaccuracy and proposes in its place the very same move. Here is an example analysis comment for my move 21... Nxd3: (-4.64) INACCURACY - Perhaps better was 21... Nxd3.