How to Check a DWG File’s Version (Without AutoCAD)

A drawing won’t open. Your software says the file is “not valid” or “from a newer version.” Or a colleague says they can’t open what you sent. Nine times out of ten, the problem is the DWG version.

DWG files aren’t all the same. Each major AutoCAD release has changed the file format over the years, and older software can’t read newer formats. Knowing which version a file is in tells you exactly what’s going on and what to do about it.

The good news: you can check a DWG’s version in about ten seconds, with no CAD software at all.

Why DWG versions matter

Autodesk updates the DWG format every few years. Each new format adds support for new features. Software built for an older format usually can’t open a newer file, because it doesn’t understand the new structure.

So if a drawing was saved in the 2018 format, a program that only reads up to the 2013 format may refuse it. The file isn’t broken. The software is simply too old for it.

Newer software, on the other hand, opens older files without trouble. Compatibility only breaks in one direction. Old files open in new software. New files often fail in old software.

The quick method: read the first six characters

Every DWG file starts with a short code that names its format. It’s always the first six characters of the file, and it always starts with “AC.” You can read it with a plain text editor.

On Windows

1. Right-click the DWG file.
2. Choose Open with, then Notepad.
3. Look at the very first characters in the top left corner.
4. You’ll see something like AC1032 or AC1027, followed by unreadable symbols.
5. Close Notepad without saving.

The rest of the file looks like nonsense, because DWG is a binary format. That’s normal. You only need the first six characters.

Important: don’t save anything in Notepad. Just close it. Saving could damage the drawing.

On Mac

1. Open the Terminal app.
2. Type head -c 6 followed by a space.
3. Drag the DWG file into the Terminal window. The path appears.
4. Press Enter.

Terminal prints the six-character code, like AC1032.

On Linux

Open a terminal and run head -c 6 with the file name after it. You’ll get the code straight away.

DWG version codes table

Here’s what each code means.

Code	DWG format	AutoCAD releases that save it
AC1009	R11 / R12	Release 11 and 12
AC1012	R13	Release 13
AC1014	R14	Release 14
AC1015	2000	AutoCAD 2000, 2000i, 2002
AC1018	2004	AutoCAD 2004, 2005, 2006
AC1021	2007	AutoCAD 2007, 2008, 2009
AC1024	2010	AutoCAD 2010, 2011, 2012
AC1027	2013	AutoCAD 2013 to 2017
AC1032	2018	AutoCAD 2018 and later releases

Notice that the format doesn’t change every year. AutoCAD 2013 through 2017 all save the same 2013 format. The 2018 format has stayed in use for many releases since.

So when someone says “it’s an AutoCAD 2024 file,” the format is actually the 2018 format, code AC1032.

What to do once you know the version

If the file is AC1032 and your software can’t open it

Your software is older than the 2018 format. You have three choices:

• Update your software, or use a newer free viewer
• Ask the sender to save a copy in an older format, like 2013
• Convert it yourself with a free tool such as DWG TrueView’s DWG Convert or ODA File Converter

Our DWG TrueView guide shows how DWG Convert works.

If the code doesn’t start with “AC”

The file may not be a real DWG at all. It could be a DXF, a renamed file, or a damaged download. Try downloading it again. If it still looks odd, ask the sender to check the file.

If the code looks right but the file still won’t open

The version isn’t the problem. The file may be damaged, or the drawing may rely on missing linked files. See our guide to DWG files that won’t open for the full list of checks.

Checking the version of a DXF file

DXF files work differently. They’re usually plain text, so you can read them in Notepad without seeing gibberish. The version is stored in the header, next to a setting called $ACADVER.

1. Open the DXF in Notepad or any text editor.
2. Press Ctrl+F and search for ACADVER.
3. A couple of lines below it, you’ll see a code like AC1027 or AC1032.

The codes mean the same thing as in the DWG table above. Again, close the file without saving.

Checking a whole folder at once

If you’ve received a large set of drawings, opening each in Notepad is slow. A one-line command can list them all.

On Mac or Linux, open Terminal in the folder and run:

for f in *.dwg; do echo “$(head -c 6 “$f”) $f”; done

You’ll get a list with each file’s code next to its name. It takes a second, even for hundreds of files.

On Windows, ODA File Converter is the easiest route for large sets. It can convert a whole folder to a single target version, which often solves the problem without needing to check each file first.

Version and revision are not the same thing

People sometimes mix up two different ideas.

The DWG version is the file format, set by the software that saved it. AC1032, AC1027 and so on.

The drawing revision is the design’s history, set by the designer. Rev A, Rev B, Rev C, usually shown in the title block.

A drawing can be Rev F and still saved in the 2013 format. Another can be Rev A in the 2018 format. When something won’t open, check the format code. When something looks out of date, check the revision letter.

Other ways to see the version

In AutoCAD. Use the Save As dialog to see the default save format. AutoCAD also warns you when you open a file saved in an older format.

In some viewers. A few viewers show the format in file properties or info panels.

In file managers. Windows doesn’t show DWG versions in File Explorer by default, so the text editor method is usually fastest.

Saving to an older version

If you send drawings to people with older software, save a copy in their format.

In AutoCAD: File, Save As, then choose the format from the “Files of type” list, such as AutoCAD 2013 Drawing.

Without AutoCAD: use DWG TrueView’s DWG Convert on Windows, or ODA File Converter on Windows, Mac and Linux.

Always keep the original in its newer format. Saving down can drop features the older format doesn’t support.

Does version matter for online viewers?

Most modern viewers read every common format up to the 2018 format, since it’s been the current one for years. Our online DWG viewer opens files in the formats people use today.

Older viewers and old copies of desktop apps are where version problems usually show up. Keeping your viewer updated avoids most of them.

A real-world example

A kitchen supplier gets plans from an architect. The supplier’s CAD software is from 2015, so it reads up to the 2013 format. The architect uses a recent AutoCAD and saves in the 2018 format.

The supplier double-clicks the file and gets an error. They open it in Notepad and see AC1032. Now they know the issue in seconds.

They email the architect: “Could you save a copy in AutoCAD 2013 format?” Problem solved. No guessing, no back-and-forth about “corrupted files.”

Even better, the supplier now knows to ask for the 2013 format at the start of every project. One line in the first email saves the same problem from coming up again on every drawing.

Questions people ask

What does AC1032 mean?

It means the file uses the 2018 DWG format, saved by AutoCAD 2018 or a later release.

What does AC1027 mean?

The 2013 DWG format, saved by AutoCAD 2013 to 2017.

Can I change the version in Notepad?

No. Editing those characters doesn’t convert the file. It will just break it. Use a proper converter.

Is a newer DWG version better?

It supports newer features. For sharing, an older format can be more compatible. Many firms send drawings in the 2013 format for that reason.

Can my phone tell me the DWG version?

Not easily. Use a computer, or open the file in a mobile viewer and check its info panel if it has one.

One last tip. When you receive a new batch of drawings, check the version of one file before opening the rest. If that one is fine, the others from the same sender almost always are too, which saves you checking every file.

The short version

Open the DWG in Notepad or run head -c 6 in Terminal, and read the first six characters. AC1032 is the 2018 format, AC1027 is 2013, AC1024 is 2010. If your software is older than the file, update it, ask for an older format, or convert it. For a quick look that doesn’t care about any of this, open the drawing in our free DWG viewer.

If you need help choosing a tool to open newer files, our list of free DWG viewers compared is a good next read.