URL for the user profile? to be a subdomain or text after the slash?

I'm creating an online based system that has public user profiles for all users..

I'm wondering how to organize the URLs for these public user profiles? What could be better for the SEO and of course for the us开发者_Go百科er friendliness?

{username}.mysystem.com

or

mysystem.com/{username}

or maybe even

mysystem.com/users/{username}

Thanks in advance!

Definitely not a subdomain for SEO Purposes.

I personally prefer the last option mysystem.com/users/{username} as it gives a level of separation from the rest of the application.

This of course requires that {username} is always unique in the database. If it is not (see StackOverflow and the ability to have whatever username you like even if it's taken), then you need to add a Unique Identifier in the url string as well mysystem.com/users/{userID}/{username}

Lastly, if the site ENTIRELY revolves around the user (IE: a blogsite), then you can remove the users from the url string and just go with {username} again providing "username" is unique mysystem.com/{username}

One consideration for SEO is "do the users benefit financially if their profiles get search traffic?"

If the answer is yes, then users have an incentive to build links to their profiles. You won't have any control over the types of links they create. Consequently algorithmic penalties could be applied to your website because one bad egg is trying to increase search traffic.

If you put their profiles on sub domains, then any negative SEO will only affect the sub domain and not the test of the website.