Glossary/Drawing basics
Xref (External reference)
A drawing linked into another drawing by reference, rather than copied into it.
An external reference (xref) attaches one drawing inside another without merging their contents — the host drawing always shows the referenced file's current content, so a shared background (a site plan, a base building layout) only needs to be updated in one place.
Xrefs matter for batch tools because content that only exists via an xref isn't part of the host drawing's own block/entity data — whether a scan follows xrefs or treats them as read-only background is a meaningful setting to check.