Are https://mvnrepository.com/repos/central and http://central.maven.org/maven2/ the same maven repository (called Maven Central)?
Also there is https://repo.maven.apache.org/maven2/ which also calles itself a Central Repository.
I use mvnrepository.com as I find it more convenient, but many referencies to Maven Central in Internet lead to http://central.maven.org
Besides both sites above are for Maven2, right?
What are the analogues for Maven3?
Besides is Maven3 widely used?
As far as I know, mvnrepository is just a search site that is not maintained by the maven people directly. It's a search site as I see it. It has been around for a while. Since it contains multiple repository source to search in and lets you select which one you work with its pretty transparent and I don't see any harm there.
If you execute mvn help:effective-settings you should be able to determine what repositories are used, in case some changes where made. The current central default in maven seems to be https://repo.maven.apache.org/maven2/ - the official search interface being https://search.maven.org/
You can also look into the maven sources of the pom what config you running on.
The /maven2/ part in the Uri only means what repository format is used within. This has not changed for maven 3 (it was different for maven 1). So it's the correct and current one today, there is no maven 3 repository format. Everything new could be added to the maven 2 format (for example some search index files or checksum files).
