There are two different types of duplicate content:
1) Content that is the same between pages of the same website and
2) Content that is the same between pages of different websites.
Content duplication between pages within a single website is not so bad and is fairly common within the footer, privacy statements or other disclaimers. But, as a rule-of-thumb, keep internal duplication under 20% of the total content volume.
Content duplication between different websites is a big “RED FLAG” to Google and should be avoided at all costs.
Google will devalue any web page it finds that has plagiarized or copied content from another website and if the level of duplication is excessive, Google will extend the devaluation to the entire website or ban you entirely.
