All data of eXo Platform are stored in a Java Content Repository (JCR). JCR is the Java specification (JSR-170) for a type of Object Database tailored to the storage, searching, and retrieval of hierarchical data. It is useful for the content management systems, which require storage of objects associated with metadata. The JCR also provides versioning, transactions, observations of changes in data, and import or export of data in XML. The data in JCR are stored hierarchically in a tree of nodes with associated properties.

Also, the JCR is primarily used as an internal storage engine. Accordingly, eXo Content lets you manipulate JCR data directly in several places.