Here's a trick from Michael Partenheimer that some may find useful. You can determine what DWG format a particular DWG file is, and you can do it without AutoCAD.

Use Windows Notepad to open your DWG. In Notepad, be sure to change the default (*.txt) file filter to All files (*.*) so that your DWG is an available selection in the Open File dialog box. (Large files will take a few moments.)



Once open, you'll see computer language — except for the first six characters.

Use those characters to identify your DWG format from the following list:

• AutoCAD DWG 2013 format = AC1027
• AutoCAD DWG 2010 format = AC1024
• AutoCAD DWG 2007 format = AC1021
• AutoCAD DWG 2004 format = AC1018
• AutoCAD DWG 2000 format = AC1015
• AutoCAD DWG R14 format = AC1014
• AutoCAD DWG R13 format = AC1012
• AutoCAD DWG R12 format = AC1009
• AutoCAD DWG R11 format = AC1009
• AutoCAD DWG R10 format = AC1006
• AutoCAD DWG R9 format = AC1004
• AutoCAD DWG R2.6 format = AC1002
• AutoCAD DWG R2.05 format = AC1.50

Remember that modern versions of AutoCAD traditionally use the same DWG format for three AutoCAD releases:

• AutoCAD 2013, 2014, 2015 use DWG 2013 format
• AutoCAD 2010, 2011, 2012 use DWG 2010 format
• AutoCAD 2007, 2008, 2009 use DWG 2007 format
• AutoCAD 2004, 2005, 2006 use DWG 2004 format
• AutoCAD 2000, 2000i, 2002 use DWG 2000 format

It’s very important that you do not use Notepad to modify the contents of the DWG file. Be sure to exit Notepad without saving (or use a copy of the original DWG file to make sure).

Notes from Cadalyst tip reviewer R.K. McSwain: You can also open Notepad first, then drag and drop the DWG file into the open Notepad window to view the contents. As Michael points out, be careful not to save the file.