a. Technical Internal Duplicate Content
The Same Content Available at multiple URLS or your website
Duplicated home page at index.html / htm or index.php pages
https://example.com/index.html or https://example.com/index.php or https://example.com/home
Session ID parameters
https://example.com/services or https://example.com/services?sessionID=1246 and more
b.Hosting Related Duplicate Content
Duplicate content caused by mis-configured server settings
Example 1: No HTTP to https redirection.
http://www.example.com/ and https://example.com/
Example 2: Site available at www and non-www.
https://www.example.com/ and https://example.com/
Example 3: Indexed staging site and development sites
https://www.example.com/dev/ and https://www.example.com/
C. 3rd Party External Duplication Content
Copies or very similar versions of your content or external domains owned by 3rd parties
Example 1: Site that manually copies your work and republishes it as their own.
Example 2: Sites that create a slight rewrite of your work and publish it as their own.
D. Own External Duplicate Content
Your Content duplicated on or by other domains and subdomains you control
Example 1: Separate mobile (m dot) website without the canonical header or rel alternate declaration in the main site header.
https://www.m.example.com/ and https://www.example.com/
Example 2: International domains, subdomains or subfolders misconfigured without href=”lang” or not translated into the local language.