What is the max limit of community members in share-point 2013 OOTB? and are there settings to increase that default limit OOTB?
i think you are talking about the SharePoint Community site.
their is no specific limit on the community rather site collection limit apply to it.
MSFT support upto 2 million individual user for a site collection.You can add millions of people to your web site by using Microsoft Windows security groups to manage security instead of using individual users. This limit is based on manageability and ease of navigation in the user interface. When you have many entries (security groups of users) in the site collection (more than one thousand), you should use Windows PowerShell to manage users instead of the UI. This will provide a better management experience.
here are the other limits.
- Number of SharePoint groups a user can belong to 5,000 Supported
- Active Directory Principles/Users in a SharePoint group 5,000 per SharePoint group Supported
- SharePoint groups 10,000 per site collection Supported
- Security principal: size of the Security Scope 5,000 per Access Control List (ACL) Supported
The community site is just a site template and is still governed by SharePoint limits.
There are some limits to work around like security principles (limited to 50,000) - but it's possible to have millions of users active in your site.