Downloaded all historical data for Oslo Stock Exchange from Yahoo Finance (yfinance), and picked a random stock to check if the data corresponds with what I see on different newssites.
If I look at NAS.OL from Yahoo at 2015-10-21, the close price is about 19911 with a volume of 4232.
But if I look at the data from Euronext (the owner of the exchange) the close price is about 9330 with a volume of 10122? This is also what I see in the different newssites here.
(Was just one action in 2020-12-18, a stock split of 0.01, according to Yahoo)
If I plot the graphs they look similar, but why is the difference in numbers so big?
(Edit: This has been marked as a duplicate, but the link to the other question is over 10 years old)