About Duplicate Content

- A small amount of duplicate content can be merged in Google search results.
- Setting canonical links on duplicate content can reduce the amount of crawling.
- Google tries to solve technical duplicate content caused by urls parameters itself.
- Tag pages are not considered as duplicate content, because only a part of the content is displayed. However, it could be considered as low quality content by users.
- If the original source of duplicate content can be found, Google will try to show it in search result.
- Don't use robots.txt to block duplicate content, use canonical links.
- Duplicate content is not considered as low quality content, algorithms know it is sometimes necessary to display legal disclaimers on every pages, for example.
- There is no such things as a duplicate content penalty, but organizing content duplication on a massive scale over many sites can result in manual or algorithmic penalties.

About Scraped Content

- Google tries to find who wrote which content and tries to use the authoritative one when there is conflicting information.
- If your content is scraped by other another website, it does not lower the quality of your website.
- Don't rewrite your content to be different than scrappers, it does not help.
- If scrappers keep ranking above your site, report them in Google forums.
- If a website is a mix of content from different sources with no added value, it can be dropped from search results.
- Rewritten content is considered as low value content.
- Same content as Wikipedia won't rank higher than Wikipedia.
- Really good content about Wikipedia can rank higher than Wikipedia.
- If a website hijacks your rankings by using 302 redirects to your website pages rather than serving their own content, set a canonical link in your content as a solution.