Download the Evernote full sync specification
If you're an Evernote user, you know that most of our client apps keep a full local copy of a user's account metadata and, in some cases, all of the notes in their account. We call this synchronization.
Most third-party applications that integrate with Evernote don't need to do this, but in rare cases, you might want to build a synchronizing client. If you are building a synchronizing client, you must follow our synchronization specification to ensure that you transfer data as efficiently as possible and do not overwrite user data in the event of conflicting changes.