Which capability of AEM Sites allows authors to see what has changed on a page for version, launch, and language copies?

The ability of AEM Sites to allow authors to see what has changed on a page for version, launch, and language copies is effectively captured by the page comparison and diff view feature. This capability provides a visual representation of the differences between versions of a page, making it easier for authors to identify what has been modified, added, or removed in each iteration.

This is particularly useful for managing content updates and ensuring consistency across various versions, as well as aiding in collaborative workflows where multiple authors may be working on a page simultaneously. By enabling authors to see these changes clearly, they can make informed decisions about content revisions and approvals.

While content version history gives a record of changes over time, it may not provide the immediate visual aspect that the page comparison and diff view does. Similarly, the change log viewer typically summarizes changes but doesn't allow for a side-by-side examination of differences, and the page update tracker is more about monitoring updates rather than comparing content. This makes the page comparison and diff view the most appropriate capability for the task described in the question.