Backlinks with different number in different sites

Hi,

I saw the number of backlinks of a domain in three different sites and all three of them
should me different numbers.

Why is it so?
Is there any logic behind it?
If so, which site should I go for?

The site I checked were - https://moz.com/
https://www.semrush.com/
https://majestic.com/

Thanks.

I've seen this too. Not a huge difference though. Another thing that i noticed is that when i add new backlinks they don't quickly show up for example on Ahrefs vs SEMRush. Don't know why's that.

Each site is different..they don't all use the same algorithm. One site may scan pages at different rates than another. Who knows, it could really be a million different things. But, that's why most people use all three sources. Three sites using three different algorithms gives you three different outlooks...