user-1: The following move is considered dubvious in lichess.org opennings explorer because of the sacrifice in f7:
[FEN "r1bqkb1r/ppp2ppp/2n2n2/3Pp1N1/2B5/8/PPPP1PPP/RNBQK2R b KQkq - 0 5"]

1... Nxd5 2. Nxf7 Kxf7 3. Qf3+ Ke6 4. Nc3 Ncb4

The following explanation is given:

5 ... Nxd5?!
Immediate recapture of the pawn sometimes thought dubious, at other times theory considers it quite playable. From a positional point of view it's not considered a good move due to the creation of open lines that White can now use to aggressively attack, and for this reason it's rarely played at master level. While modern computer analysis suggests that it may be theoretically playable, few doubt that 5...Na5 is a more practical choice in an over the board game.

While I use to refuse sac lines because I am a poor player, I feel confortable with white in this line. However lichess says it is playable.
How much playable it is? Can black preserve material not being checkmated with his king on the center and the open white position?

user15223: It's playable in the sense that there is no known forced win, but the line Black has to thread to equality is a fine one. This is reflected by the opening eval, about +0.7 - +0.9 (see my answer to a different question here about how to interpret the opening eval).
It's possible Black can defend the position. Here's a game which Leela Chess Zero defends with Black, and here's another where Stockfish defends with Black. It's even possible Black wins, although this game 1) Black was clearly the stronger player and 2) the book line given to the engines after 5...Nxd5 is not the best continuation for White, hence the 0.00 opening eval.
Note computers, if left to their own devices, generally prefer 6. d4 to 6. Nxf7.

user11144: Black is not in danger of being mated, but still, in the "standard" variants, Black also loses the e-pawn, thus having only +1 material, a huge developmental disadvantage, and a king on the run. In my youth, I blitzed this opening with both sides and always won, but that was because I was the best player in my club. If you are willing to suffer, go forth. The Lichess percentage is atrocious (+50=20-30) but Stockfish is unimpressed playing Black.

-1: <p>The following move is considered dubvious in lichess.org opennings explorer because of the sacrifice in f7:</p>
<pre><code>[FEN &quot;r1bqkb1r/ppp2ppp/2n2n2/3Pp1N1/2B5/8/PPPP1PPP/RNBQK2R b KQkq - 0 5&quot;]

1... Nxd5 2. Nxf7 Kxf7 3. Qf3+ Ke6 4. Nc3 Ncb4
</code></pre>
<p>The following explanation is given:</p>
<blockquote>
<p>5 ... Nxd5?!</p>
<p>Immediate recapture of the pawn sometimes thought dubious, at other times theory considers it quite playable. From a positional point of view it's not considered a good move due to the creation of open lines that White can now use to aggressively attack, and for this reason it's rarely played at master level. While modern computer analysis suggests that it may be theoretically playable, few doubt that 5...Na5 is a more practical choice in an over the board game.</p>
</blockquote>
<p>While I use to refuse sac lines because I am a poor player, I feel confortable with white in this line. However lichess says it is playable.</p>
<p>How much playable it is? Can black preserve material not being checkmated with his king on the center and the open white position?</p>
 15223: <p>It's playable in the sense that there is no known forced win, but the line Black has to thread to equality is a fine one. This is reflected by the opening eval, about +0.7 - +0.9 (see my answer to a different question <a href="https://chess.stackexchange.com/questions/32402/stockfish-evaluations/32403#32403">here</a> about how to interpret the opening eval).</p>
<p>It's possible Black can defend the position. Here's a <a href="https://tcec-chess.com/#div=s16lczero_redfish&amp;game=16&amp;season=bonus" rel="nofollow noreferrer">game</a> which Leela Chess Zero defends with Black, and here's <a href="https://tcec-chess.com/#div=sf&amp;game=44&amp;season=15" rel="nofollow noreferrer">another</a> where Stockfish defends with Black. It's even possible <a href="https://tcec-chess.com/#div=vsob10&amp;game=15&amp;season=16" rel="nofollow noreferrer">Black wins</a>, although this game 1) Black was clearly the stronger player and 2) the book line given to the engines after 5...Nxd5 is not the best continuation for White, hence the 0.00 opening eval.</p>
<p>Note computers, if left to their own devices, generally prefer 6. d4 to 6. Nxf7.</p>
 11144: <p>Black is not in danger of being mated, but still, in the &quot;standard&quot; variants, Black also loses the e-pawn, thus having only +1 material, a huge developmental disadvantage, and a king on the run. In my youth, I blitzed this opening with both sides and always won, but that was because I was the best player in my club. If you are willing to suffer, go forth. The Lichess percentage is atrocious (+50=20-30) but Stockfish is unimpressed playing Black.</p>
