If you’ve ever pushed an updated block to a network drive only to find half your team still inserting the old version, you’ve felt the frustration. AutoCAD doesn’t "live link" to external block files by default—it caches them locally.
However, there is a powerful (and often overlooked) method to force AutoCAD to recognize updated source files: The Block Host File (the $m macro and trusted paths). autocad block host file updated
In this post, we’ll break down how to set up a "host file" system for your blocks so that when you update a master drawing, everyone’s inserts update automatically. Change log
While this feature is generally beneficial, it increases the file size of the Host drawing. Communication
The message often appears because AutoCAD saves the host file every time you exit the Block Editor.
If you meant how to update the content inside a block (like editing text or attributes):
How to Update Block Definitions: