Yandex metrica vs Vk statistics. Who to believe?

Question

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VK advertising statistics say that there are 500 clicks, and Yandex Metrika says 250 visits. Whom to believe or do they show different things?

Answer 1

Yandex can consider 10 clicks from one IP as not unique + statistics in the yash is not immediately issued

Answer 2

It turns out that there is a big difference between clicking on a banner and going to a website. AdRiver did a lot of research and found out that about 50% of clicks in current RuNet advertising campaigns do not lead to a transition to the site! These users are referred to as "missers". About where they come from and who they are in general, read the article Where are the clicks going? on cossa.ru

Answer 3

Parse the logs yourself and analyze for all monitoring systems.

Answer 4

To sketch on PHP itself accounting for statistics of exactly what needs to be taken into account. It will be 100% reliable, because in PHP there will be exactly as many records as the number of times the page was loaded.
Personally, I did just that and I look at what I need.