user16626: I played a game starting with

d4 d5 2. c4 dxc4 3. Nc3 a6 4. a4 Nc6 5. Nf3

Black's next move is 5... Bg4 and it was considered by chess.com as

Inaccuracy (-0.28) A better move was 5... e5 (5... e5 6. d5 a5 7. e4
  f6 8. e2 b4 9. g5 O-O 10. O-O)


But according to 365chess.com, the move 5... e5 is seldom played while 5... Bg4 is more popular with a high winning percentage for black. Why does chess.com consider 5... Bg4 as an inaccuracy?



user12629: Chess.com listed this as an inaccuracy because the engine is running at a limited depth, only looking at each move for a few seconds. 
When I put the position after 5...Bg4 into Stockfish, it gave an evaluation of +0.12 at 16 ply. But at 18 ply, the evaluation dropped to -0.38. Most likely if you had run the analysis at "maximum" (which I realize is locked for non-premium members) the engine would have analyzed enough to know that 5...Bg4 was not an inaccuracy.

16626: <p>I played a game starting with</p>

<ol>
<li>d4 d5 2. c4 dxc4 3. Nc3 a6 4. a4 Nc6 5. Nf3</li>
</ol>

<p>Black's next move is 5... Bg4 and it was considered by chess.com as</p>

<blockquote>
  <p>Inaccuracy (-0.28) A better move was 5... e5 (5... e5 6. d5 a5 7. e4
  f6 8. e2 b4 9. g5 O-O 10. O-O)</p>
</blockquote>

<p><a href="https://i.stack.imgur.com/njbq0.png" rel="noreferrer"><img src="https://i.stack.imgur.com/njbq0.png" alt="enter image description here"></a></p>

<p>But according to 365chess.com, the move 5... e5 is seldom played while 5... Bg4 is more popular with a high winning percentage for black. Why does chess.com consider 5... Bg4 as an inaccuracy?</p>

<p><a href="https://i.stack.imgur.com/7EMRv.png" rel="noreferrer"><img src="https://i.stack.imgur.com/7EMRv.png" alt="enter image description here"></a>
<a href="https://i.stack.imgur.com/colJ1.png" rel="noreferrer"><img src="https://i.stack.imgur.com/colJ1.png" alt="enter image description here"></a></p>
 12629: <p>Chess.com listed this as an inaccuracy because the engine is running at a limited depth, only looking at each move for a few seconds. </p>

<p>When I put the position after 5...Bg4 into Stockfish, it gave an evaluation of +0.12 at 16 ply. But at 18 ply, the evaluation dropped to -0.38. Most likely if you had run the analysis at "maximum" (which I realize is locked for non-premium members) the engine would have analyzed enough to know that 5...Bg4 was not an inaccuracy.</p>
