“Can you open this?” is the most common question at the start of a CAD conversion job, and the honest answer depends on a detail most people never see: the DWG format version written inside the file, which is not the same as the AutoCAD release that produced it. This page is the reference table we use in-house when a client sends a file an older seat cannot read.
Release year is not format version
Autodesk changes the DWG file format roughly every three releases, not every year. Several consecutive AutoCAD releases therefore write the same format, and a file from a much newer release can open perfectly in an older seat as long as both sit inside the same format generation. The rule is simple and one-directional: a CAD application can read its own format version and every older one, but it cannot read a newer one.
DWG format versions and the releases that write them
| DWG format | AutoCAD releases that write it | Opens in |
|---|---|---|
| AC1032 (DWG 2018) | AutoCAD 2018 through 2026 | 2018 and later only |
| AC1027 (DWG 2013) | AutoCAD 2013 – 2017 | 2013 and later |
| AC1024 (DWG 2010) | AutoCAD 2010 – 2012 | 2010 and later |
| AC1021 (DWG 2007) | AutoCAD 2007 – 2009 | 2007 and later |
| AC1018 (DWG 2004) | AutoCAD 2004 – 2006 | 2004 and later |
| AC1015 (DWG 2000) | AutoCAD 2000 – 2002 | 2000 and later |
| AC1014 (R14) | AutoCAD R14 | R14 and later |
DWG 2018 has been the current format for an unusually long run of releases, which is why cross-version problems are less common now than they were a decade ago. The files that still cause trouble are the old ones — archive drawings in R14 or DWG 2000 format that carry proxy entities from applications no longer in use.
How to check what version a file actually is
- Without opening it: the first six characters of a DWG file are the format code —
AC1032,AC1027and so on. Any text editor or hex viewer will show them. - In AutoCAD: the format is reported when the drawing is opened, and Save As shows which format the current file will be written to.
- In bulk: for a folder of archive drawings, reading the first six bytes of every file is far quicker than opening them one at a time.
DXF: the interchange format, and its own trap
DXF was designed for interchange between applications and tracks the same version generations as DWG. It is the safer choice when the receiving application is not AutoCAD — most CAD and CAM systems read DXF more reliably than DWG. Two things to know before you send one:
- DXF is lossy for some content. Custom objects, some dynamic block behaviour and application-specific data may not survive the round trip. Geometry, layers, text and dimensions generally do.
- ASCII versus binary. ASCII DXF is human-readable and much larger; binary DXF is compact but not every application accepts it. When in doubt, send ASCII.
What to send, and what to ask for
- Sending to an unknown recipient: DWG 2010 format is the safest common denominator — old enough that almost everything opens it, new enough to carry modern annotation.
- Sending to a laser cutter, waterjet or CNC: DXF, geometry only, in millimetres, with the profile as closed polylines on a clearly named layer.
- Archiving: keep the native DWG at the version it was authored in, plus a PDF of the issued sheet. The PDF is what survives when the CAD application does not.
- Receiving a file you cannot open: ask for it to be saved down, and say which format version you need. “Save as an older version” without a number usually comes back one generation down, which may still be too new.
When saving down is not enough
Saving a drawing to an older format converts what it can and substitutes what it cannot. Objects created by a vertical application — a steel detailing add-on, a plant modeller, a survey package — become proxy entities that display but cannot be edited, and can be lost entirely on the next save. Where that matters, the drawing needs to be redrawn as native geometry rather than converted.
That is the work our CAD conversion services exist for: rebuilding a legacy or proxy-laden drawing as a clean, editable, layer-correct file rather than passing on a file that merely opens. For scanned and hard-copy originals, paper to CAD conversion is the equivalent process; for cross-platform work, see DWG to DGN conversion.
Drawing presentation — sheet sizes, title blocks, line types and text heights — is governed in Australia by AS 1100, published by Standards Australia. A converted file that opens but does not conform to the drawing standard is only half the job.