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MACD is a momentum indicator but you don't use it to measure oversold / overbought conditions. Its not range bound like RSI, W%R, Stoch etc so there's no way to measure 'oversold'. Is it 'oversold' when it's -0.1 ? -0.2 ? -0.745 ? -23.7 ? It just doesn't work like that.

You use it to see the trend direction and strength of the past (it's a derivative of a derivative of a derivative, about the laggiest indicator you can get). Easier just looking at the actual price chart unless you're using it for some divergence indication or something.

Is it 'oversold' when it's -0.1 ? -0.2 ? -0.745 ? -23.7 ?

Without a chart it is impossible to guess only from those numbers.

But have you ever tried on using MACD extreme highs and lows?

Here is a good source to understand about MACD:

https://www.investopedia.com/terms/m/macd.asp

And how to use MACD Divergence to find a possible reversal.

https://www.investopedia.com/articles/forex/05/macddiverge.asp

And some other ways on how to use MACD

https://www.investopedia.com/articles/technical/082701.asp

You Will notice that none of them mention oversold/overbought

I was more like interested in MACD as a tool for oversold/overbought conditions. There are more articles about it, but this one looks quite explanatory.

No, because that doesn't make sense. It may be -0.5 now, but what if it carries on falling to -1, or -5 ? What if the market becomes very volatile for a long time and -3 becomes the new 'extreme' ? If you look on the chart above from Aug to Dec the 'extreme' was only -0.1 that whole time. At what point then was it considered overbought/oversold ?

It's not a bounded range, it's an absolute value with no limits that changes all the time so you can't really quantify it and say 'x level mean oversold'. I think the OP is confused between a downtrend and being oversold. You can still be overbought in a downtrend ! Infact that's exactly what people wait for to enter trades...