I suspect you overlooked the black rook on a7
How is this a blunder!?
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What is a blunder?
However, never assume a machine will always calculate the correct thing. They can, but it will probably talk to you and say "No" 
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Rxe7 is easily winning because the White queen is placed in a very dangerous position for the Black king. If the game follows 1...Rxe7 2. Rxe7 Qxe7 3. d6+ Qf7, then 4. Bd5 finishes the queen.
ajl721x, if the Black queen captures the hanging knight on b6, then Black's doom will come even more quickly i.e. 1. Rxe7 Qxb6? 2. d6+ and it's sayonara for Black.
The main reason why the computer labels this a blunder is because the best move available is better than your played move by many points, even if your played move is still winning. I would personally play the same move 1. Rxe7 rather than the best possible move 1. Re6 (which technically looks like a mouse-slip of 1. Rxe7).
P.S. I wonder how the White knight managed to land on the b6 square.
Jan 14, 2021
0
#5
In other words, while the engine recommends the “best” move (Re6), it requires more work than necessary to follow up and win. In human perspectives, such calculations make things more difficult.
I would be more than happy to play the tempting and practical Rxe7. White is still easily winning with this move, only this time he/she doesn’t have to arduously calculate more variations. You’re fine over here.
It's a mistake because you had a better move. Your move isn't losing but if you played Re6 first you have a stronger attack. If you are using the basic anaylsis the engine might call it a blunder instead of a mistake or whatever.
But in the end the analysis is good and your interpretation isn't. It's a computer, if you can't understand why it doesn't like your move and it makes you cry about it, then don't use it.
i actually think it is a mistake because after threatening the black queen with the bishop as proposed by eric0022 the black can take it with the rook in d8 and taking back with the queen means losing it, after that black can add pressure on the queen with Kc6
Huh wdym blunder
on my screen it says its good
or maybe its only your chess.com engine...
Jan 15, 2021
0
#9
Laskersnephew wrote:
I suspect you overlooked the black rook on a7
No black couldn't recapture the rook on e7 because of this:
Edit: Sorry I forgot to add the white king into the diagram lol
Don't worry, man. You had to play Re6 here to continue the engine line. Rxe7 goes from +6.5 or something to +5.5 something, so it's completely okay, as long as you keep your back rank defended. It's a pretty human move to make. 
Jan 15, 2021
0
#11
Theasker wrote:
i actually think it is a mistake because after threatening the black queen with the bishop as proposed by eric0022 the black can take it with the rook in d8 and taking back with the queen means losing it, after that black can add pressure on the queen with Kc6
Unh uh! the pawn on d6 will block any capture by the rook on d8.
Jan 15, 2021
0
#12
I'm thinking the analysis only really gives spot on advice on pure positional play. I have had a couple of games now, when I deliberately sacrificed pieces for a win, but the analysis said these were bad moves.
Toxitalk 写道:
I'm thinking the analysis only really gives spot on advice on pure positional play. I have had a couple of games now, when I deliberately sacrificed pieces for a win, but the analysis said these were bad moves.
Or maybe you didn’t realise that it actually does not win
show a example game
Jan 15, 2021
0
#14
It’s not what we’d normally call a blunder because you are still winning, a knight up, after that combination since queen can’t take on e7, and will instead probably move king to break the pin. However black has some counter play re attacking the white knight, which needs rescuing.
However the engine views it as a blunder because Re6 instead gives you a better winning position
However the engine views it as a blunder because Re6 instead gives you a better winning position
Jan 15, 2021
0
#15
tacticspotter wrote:
Toxitalk 写道:
I'm thinking the analysis only really gives spot on advice on pure positional play. I have had a couple of games now, when I deliberately sacrificed pieces for a win, but the analysis said these were bad moves.
Or maybe you didn’t realise that it actually does not win
show a example game
I would have to look back, but in each case the opponent took the sacrifice and I then they resigned within a move. It might be that the computer saw further lines, but as said it was enough to cause my opponents to resign.
Toxitalk 写道:
tacticspotter wrote:
Toxitalk 写道:
I'm thinking the analysis only really gives spot on advice on pure positional play. I have had a couple of games now, when I deliberately sacrificed pieces for a win, but the analysis said these were bad moves.
Or maybe you didn’t realise that it actually does not win
show a example game
I would have to look back, but in each case the opponent took the sacrifice and I then they resigned within a move. It might be that the computer saw further lines, but as said it was enough to cause my opponents to resign.
You probably played against people your rating,which saw the same thing as you so they resign
OK???
toaster-man wrote:
Here in this posision I played as white Rxe7 and in the analysis the chess.com chess engin (whatever engin that is) says its a blunder. is it? or is chess.com analysis engin just sh..t.
Thank you!
After he takes your rook with his rook, You have to give up another rook or he will play Rxe1 checkmate, if you move your rook he will take you hanging horse and there is nothing you can do about it
Toxitalk wrote:
I'm thinking the analysis only really gives spot on advice on pure positional play. I have had a couple of games now, when I deliberately sacrificed pieces for a win, but the analysis said these were bad moves.
there is a hanging horse also
What defines a blunder?
My engine shows an additional 7 points for white for Re6 in favor over Rxe7. Someone, somewhere said that leaving 7 points on the board is a blunder. How about 6? How about 3.521?
Does it matter if it ends in having a 0.1 advantage vs 7.1? Or 30.0 vs 37.0?
More often then note, I end up with terrible blunders complete with ?? annotations when I run my games through my local engine for automatic analysis and I'm in a winning position. I find it instructional to look at those to see if there's a way to be more efficient. Was there a better response my opponent could have made to what I chose that would have hurt me? Or is it merely a matter of taste? Do I want to mate in 13 moves or 16?
My preferred engine says that move changes white's odds of winning from 98% to 95%. I'll take the 95% and simplifying the board.
Here in this posision I played as white Rxe7 and in the analysis the chess.com chess engin (whatever engin that is) says its a blunder. is it? or is chess.com analysis engin just sh..t.
Thank you!