Does a maven repository have a standard format?

Question

How are repos laid out? Are they the same? If so, who specifies the format.

Answer 1

Repository layout for Maven is defined very strictly. Maven itself is the tool that completely handles the repository.

/$groupIdWithSlashes/$artifactId/$version/$artifactId-$version.$extension
/$groupIdWithSlashes/$artifactId/$version/$artifactId-$version-$classifier.$extension

Read more here on details of the layout, and here on details of metadata files.

Note that Nexus has similar layout in its storage, but (in some cases) slightly different format of metadata.xml file.

Other repository managers can have completely different layout in its internal storage - like Artifactory. Anyway, the URL structure must be (and is) identical.