What Is an Xref (External Reference) in AutoCAD?

An attached xref travels with its host. If the electrical plan attaches the architectural background, and a lighting sheet then attaches the electrical plan, the architectural background comes along as a nested reference. An overlaid xref stays behind, so it shows in the drawing that overlays it and nowhere further down the chain.

Many firms overlay backgrounds from other disciplines for that reason. Overlay keeps a background from appearing twice on a sheet that already references it directly, and it avoids circular references when two consultants reference each other's files.

A full path stores the drive and folders, such as P:\Projects\Riverside Hotel\Backgrounds\Arch-L2.dwg, and breaks when the project is archived, moved, or opened by a consultant with a different drive letter. A relative path stores the location relative to the host, such as ..\Backgrounds\Arch-L2.dwg, and keeps working as long as the folder structure stays intact.

No path stores only the file name, and AutoCAD searches the host folder and the support search paths. That suits a transmittal package with everything in one folder. A Not Found status in the palette usually points to a path problem, and the file itself is usually sitting one folder away.

Binding converts an xref into a block in the host drawing so the drawing can be sent as a single file. With Bind, layers and other named objects are renamed with the xref name and a number, such as Arch-L2$0$A-WALL, which keeps them apart from host layers. With Insert, they merge into host layers of the same name.

A bound drawing no longer updates. That is what an issued set or an archive needs, and a problem when someone keeps drafting on a bound copy while the architect keeps revising the original. The BINDTYPE system variable controls which naming method applies by default.

Freezing or recoloring Arch-L2|A-FURN in the host leaves the architect's file untouched. With the VISRETAIN system variable at its default of 1, those overrides are saved in the host and survive a reload.

In a layout, VP Freeze hides an xref layer in one viewport only, which is how one background shows furniture on an enlarged plan and hides it on the power plan. Screening architectural linework under MEP work is usually done with xref layer colors that the plot style table prints at a halftone.

XCLIP limits the visible area of an xref to a boundary, so an enlarged plan shows only the restroom from a full-floor background. The clip lives in the host, and the full reference stays intact underneath.

The palette flags an xref that changed since it was loaded, and Reload brings in the new version. A sheet plotted without a reload can show last week's walls under this week's electrical layout, so many firms reload all references as a standard step before plotting an issue.