Explaining the moves is a very difficult problem, in a sense the "line" (series of moves) the computer recommends as best for both players is the explanation. Translating that information into, say, english, or some sort of useful graphical format, would be a pretty novel feature.

https://decodechess.com/ does that kind of thing.

I think the problem here is that chess engines are going to recommend 'non-human' moves at any point of the mid/endgame. And these 'non-human' moves could be the first/second/third best moves according to the engine. You'd have to have to have decent understanding of the game to realize what moves aren't going to blow your cover. I am confident over the long run anti-cheating software could pick this up in most cases. But also what are the incentives for someone to cheat at online chess over the long run? It wouldn't be that interesting for more than a couple days to get a quick thrill of beating a bunch of people in my opinion.

An easy way to detect cheaters is to look at overall accuracy as some aggregate metric of deviation from 'optimal' (as per the engine(s) used). This could just be a average of squares of centipawns lost per move, or classifying moves like how chess.com does (brilliant/best/excellent/good/inaccuracy/mistake/blunder/missed-win) and then looking at average distributions from this.

You can also just use the computer for the opening. If you don't have a certain opening, or response to a certain opening memorized, just use a computer. The difference between a memorized opening and what a computer would suggest is basically nil.

This is the only sort of cheating suggested in this thread that wouldn't be caught, but wouldn't actually be that helpful.

It's pretty helpful for the average human. Most people can't blast out 15 moves of theory correctly for every possible opening, so you'd avoid a lot of bad middle games or losses to traps.

It probably isn't as helpful to a grandmaster, but that's true of engine analysis in general

Unless you're very careful I think it should be detectable at those levels. If someone is taking the same amount of time when playing some rare and tricky opening line as they are when playing the QGD, that's pretty fishy if they don't have the level where you have a big variety memorized.

> It's pretty helpful for the average human. Most people can't blast out 15 moves of theory correctly for every possible opening, so you'd avoid a lot of bad middle games or losses to traps.

Yeah, although at that level lots of people are also getting into good positions, having no idea why it is good, and losing it.