How does VKontakte find out about the search queries I searched for in Yandex?

Question

contextual advertising

Good day, gentlemen.
Such a question arose. For example, I type in the Yandex search engine "English language courses in Moscow", I start searching, browsing sites, etc. And literally after 10-15 minutes, ads strictly on the subject of my request begin to flicker in VK ad blocks.
However, when you create an advertisement, VK does not even have a hint of search targeting (for example, to write down key phrases of interest, etc.).
Actually, it is not entirely clear how exactly the social. Is the network tracking my searches? There are some assumptions, but in general there is no idea how this is implemented (referrer, cookies, etc.).

Answer 1

Yandex is an advertising partner of VKontakte and pushes its own banners into targeted advertising (which is under the left menu). Remarkably, such banners have different and softer restrictions on the number of characters in the description and title than those that VKontakte imposes on you when creating an ad, and such banners may even violate the VK rules themselves. For example, VKontakte prohibits addressing users in targeted advertising to "you", but Yandex banners often ignore this point. Thus, it cannot be ruled out that Yandex has some kind of internal algorithms or agreements with VK that allow it to form a retargeting group based on search queries alone.
Actually, more about the retargeting group. Site owners set "pixels" (a 1 by 1 pixel image) in the page markup in the tag <img>, which are hosted on VKontakte servers. When a user uploads this picture, VKontakte determines the user ID using cookies and adds it to the retargeting group. You can then show ads to that group.
It is not uncommon for site owners to sell pixel space to other companies so they can display more relevant banners. Let's say you are the owner of a forum about vacuum cleaners. Some trading network, for example, MVideo or Ulmart, can rent from you the placement of its pixel, which will collect a retargeting base for them. And then they will show your audience an advertisement for their products (vacuum cleaners) on VKontakte.