Is there a spoiler/slider effect on indexing?

Question

Search Engine Optimization

Good day!
There is a blog, in the output of posts with full text,
styles make a spoiler (display: none; ), in which part of the content is hidden and can be expanded by clicking. There is no separate page with full, not hidden text.
So, I'm wondering how the search engines react to this? Do they index what is hidden or do they downvote a lot?
I tried to experiment and hide the text almost entirely under the spoiler - some pages appeared in the index, some didn’t, in general I didn’t understand how strong the influence was, most likely not enough time had passed.

Answer 1

Both search engines index everything, incl. and what's in display: none. But ranking is another story: Google, after switching to mobile first, the content that is under the cut, in accordions and on sliders, ranks worse, there were studies a year and a half ago. But Yandex does not care, it ranks such text as normal.