3.3External references (Xref), images & PDF/DWG underlays
On a real project, you never work alone in a monolithic file. External references (Xref) let you attach a DWG drawing inside another, like a linked layer: the architect's background, for example, appears in the electrician's file. The Xref remains a separate file: if the original changes, the reference updates.
It's the foundation of teamwork and multi-discipline coordination. You can also integrate images (raster) and PDFs as underlays to align a drawing on a scanned background or a provided plan. Well managed (paths, layers, clean detach), Xrefs keep files light, consistent and up to date. Poorly managed, they create broken links: hence the importance of method.
Section vocabulary
- External reference (Xref)
- DWG drawing attached in another drawing, remaining a separate file, updated if the original changes.
- Attach / Overlay
- Attach: the Xref follows in nested Xrefs. Overlay: it doesn't propagate to higher levels.
- Underlay
- Image, PDF or DWF integrated as a reference background, non-editable, used as support (alignment, scanned background).
- Reference path
- Location of the linked file. A broken path (moved file) breaks the Xref: handle with care.
- External References Manager (XREF)
- Palette to attach, detach, reload and manage the state of references.
What is an external reference (Xref)?
In practice — Working with external references
- Attach a DWG as an Xref (XREF command or drag-and-drop): it appears as a linked background.
- Modify the original file, come back, and reload the Xref: notice the update.
- Integrate a PDF or an image as an underlay to align a drawing on a provided background.
- Manage the paths in the External References Manager and cleanly detach an unnecessary Xref.
Key points to remember
- An Xref attaches a DWG into another, remaining a separate file (updated if the original changes).
- It's the foundation of teamwork and multi-discipline coordination.
- Images and PDFs can serve as underlays (alignment, background).
- Managing paths avoids broken links.
Frequently asked questions
Xref or insert the drawing as a block?
The Xref stays linked to the source file: if the architect updates their plan, your background updates automatically — essential in collaborative projects. An inserted block freezes a copy at a point in time, without a link. For a shared background that evolves, always use an Xref. For a standard component that doesn't move, a block is enough.
My Xref disappeared / shows a broken link, what should I do?
It means the linked file was moved, renamed or deleted: the path is broken. In the External References Manager (XREF), find the reference in error and redefine its path to the correct file, then reload. To avoid this on shared projects, relative paths and a stable folder organization are often preferred. Rigorous path management is the key to Xrefs.