For example, what do you find hard to find on Google search engine, or some other custom search engines (e.g. on e-commerce websites)?
Not to mention that although popular search engines should largely the same, they are slightly different in relevancy. (And somehow Google Search is slightly better...)
Perhaps this topic is also about full-text indexing and NLP in general.
There are also other aspects in relevancy, like indexing the images' meaning? videos? colors itself?
Latest comments (6)
crawling SPAs :/
Try some prerendering services.
Well, the most thing I found really annoying in google (the only search engine I use actually) as a developer is the lack of support for non-alphanumeric characters.
Sometimes you want to search for a small block of code you found on StackOverflow or a very specific error message from a famous framework but you can't, since it contains a lot of non-alphanumeric stuff.
Related.
Why isn't it open to criticism?
I found later that there is how it works -- google.com/search/howsearchworks/a...
Though, I do also hear about black hat SEO and evasions. So, how much is the black list affected? What is manual, and what is automated?
Also, I am currently interested more in indexing limitations, and full-text-search limitations. Don't focus too much on "Google LLC". (Although I am indeed interested in why do Google, Bing, Yahoo, DDG give different results.)