How illegal is it to use someone else's content?

Question

Blogs

Good evening guys!
I have been thinking about the idea of ​​a web service for a long time - a cataloger of articles, news, etc., etc. in one service. The service will parse two dozen sites in a timely manner and select good materials. I think Yandex is doing something similar. Of course, in order to avoid mats on the part of the authors, there will be all sorts of copyrights and links. But is this enough? How legal or illegal is it?
At the moment, I am already developing the core of the service (analysis of the similarity of materials, search, categorization and tags).
With a high probability there will be clients for devices.

Answer 1

there will be complaints. and a lot.
1) copyright is not enough. there are a lot of sites where authors are against copying content. even with attribution.
2) if you parse, then there is a great chance that search engines will index your page earlier than the original one - complaints about the search engine will come from here - and then the search engines will simply throw you under the filter.

Answer 2

if you write annotations and then a link to a third-party res, then it’s normal, 1 in 1 quotes are generally not, but for a couple of paragraphs you can

Answer 3

Be sure to link to the source.

Answer 4

If we are talking about copying original copyright content, even with a link to the source, then I don’t see the point of launching this site at all ...