Now that my upcoming book AutoCAD 2015 and AutoCAD LT 2015: No Experience Required is off to the printers I can (hopefully) begin giving my blog the attention it deserves. I look forward to sharing some new tips & tricks I have been gathering for some time in some future blog posts, but first a quick tip for controlling the way AutoCAD drawings open when you double-click on a file from Windows Explorer. The behavior most AutoCAD users expect is double-clicking a DWG file will do one of two things; launch AutoCAD if it’s not already running, or open the DWG in an existing AutoCAD session.

Although all current versions of AutoCAD allow for multiple drawings to be open at once, some AutoCAD users have observed double-clicking a drawing from Windows Explorer will open the drawing in a new session of AutoCAD instead of an existing session of the application. There are two settings to check if you run into this issue:

Single Document Interface (SDI)

Although all current versions of AutoCAD can open multiple drawings at once, this hasn’t always been the case. It’s rare for the setting to get changed, but the SDI variable controls whether AutoCAD opens every drawing in a new session of AutoCAD, or allows multiple drawings to be opened in a single session. To verify multiple documents are supported in AutoCAD:

  1. Enter SDI at the command-line.
  2. At the Enter new value for SDI: prompt, enter “0”

Set the Default Application to open DWG Files

While it’s certainly possible the SDI variable was changed from its default value of 0, the more common cause to drawings opening in a new session of AutoCAD is related to the application associated with DWG files on your computer. Although it might seem logical to set AutoCAD as the default program for DWG files, doing so will cause every drawing to open in a new session of AutoCAD. Instead, the default program associated with DWG files should be the “AutoCAD DWG Launcher”.

To set the “AutoCAD DWG Launcher” as the default program for DWG files:

  1. Locate a DWG file in Windows Explorer.
  2. Right-click on the DWG file and select Properties.
  3. On the General tab of the Properties Dialog, select the “Change” button next to the “Opens With” property.

    Windows File Properties Dialog TCG Properties

    Windows File Properties Dialog

  4. Locate “AutoCADDWG Launcher” within the “Opens With” dialog, and click OK.

    Windows Open With Dialog TCG OpenWith

    Windows Open With Dialog

Double-clicking DWG files from Windows Explorer should now open drawings in a single session of AutoCAD.