DWG Files — 7 Things You Need to Know

Updated Oct 14, 2018
DWG Files - Person Drawing Sketch

From the commonly mistaken origins of the Drawing file format, to its remarkable ability in making complicated designs practicable, we’ve documented 7 of the most extraordinary things you need to know about DWG files.

1. DWG wasn’t initially designed for Autodesk


AutoDesk Logo

Most people think that the DWG file type came directly from CAD market leaders, Autodesk. But that isn’t exactly what happened.

Mike Riddle was the programmer responsible for the Drawing format. Back in the late 1970s, Riddle found that contemporary CAD programs simply “weren’t going to cut it”, and set out to devise a solution. He launched Interact in 1979, and it became the world’s first software to utilize DWG as its native file type.

But Interact CAD turned out to be limiting; its memory was small, and—in its original form—it failed to make any real impact on the industry. The program sold only around 30 copies, before Riddle took it to his friend, John Walker.

The software silenced Walker—somewhat of a rarity, if Riddle’s account is to be believed. He pronounced it a “portion”: something with which to work on and develop into something even greater. Even Walker didn’t realize the full potential of the product, though; he didn’t pay Riddle up front for the rights, opting instead for a less risky approach. Riddle came away from the deal with the promise of 10% of any program devised from the file he’d designed. Neither could know how lucrative the code would turn out to be.

Riddle, Walker and some other programmer friends banded together to start a new company: Autodesk. They used Interact, along with its DWG file type, to form the backbone of an advanced program; one that was going to change the world on design. In 1982, AutoCAD was born.

Learn more about the history and future of DWG files here.

2. They’re the subject of an ongoing power struggle

Binary code

Binary code is presented as 1s and 0s, which makes it difficult to decipher

The control over DWG technology has long proved to be a contentious issue. Autodesk have always chosen to keep the file specifications a closely guarded secret—and this has angered some competitors.

The file information is stored as binary data, which makes it intentionally difficult for others to read or make sense of. In 1998, a group of like-minded individuals joined forces to form a non-profit organization called the Open Design Alliance, which aimed at promoting the accessibility of CAD data. They hoped to reverse engineer the DWG file and eliminate the exclusivity Autodesk held over it. The first part of this mandate went, more or less, to plan: their version of DWG is available for free on the web.

In return, Autodesk issued a popup to display a strong warning—watered down in 2007, following a legal dispute—to users opening files not licensed by themselves. Their message was simple: compatibility would be compromised. In other words, no other option was good enough to successfully replace an Autodesk DWG file.

However, despite their extensive authority over the file type, Autodesk have thus far failed in attempts to trademark DWG, which would allow them to monopolize the format entirely. It’s a power struggle Autodesk hoped to avoid with the development of DXF files, the specifications of which it publishes online.

3. You don’t need to own AutoCAD to edit DWG files

Instead of sharing DWG files, Drawing Exchange Format (DXF) files are often used for collaboration between different companies along the design process. This is because the open-source DXF format is compatible with almost every CAD program in the world. However, there are dangers of converting to DXF—primarily, that information may be lost en route.

To avoid this, it is sometimes preferable to keep complex files in their native state. So, what should you do to ensure that the different players involved in a project are able to open and revise the file?

The idea that splashing out on AutoCAD is the only effective way to work with DWG files is (thankfully) a myth. You may already be aware that Autodesk actually offers 3 different types of free software: A360 Viewer, DWG True View and AutoCAD 360. All of these can be used to view DWG files without AutoCAD, and even perform some minor edits. 

Scan2Cad logo But there are limitations. That’s partly what prompted Scan2CAD to release software that allows you to both view and extensively alter drawing files, using a full suite of editing features.

We are, of course, biased—but you don’t have to take our word for it. Sign up for a free 14 day trial to test our claim.

4. Less storage space is eaten up

We already discussed one benefit to DWG’s use of binary coding: it allows Autodesk to retain a competitive advantage, because it is difficult for others to ascertain how the information within the file is stored.

However, it also provides a clear asset to the user. The use of 1s and 0s, as opposed to plain text or ASCII, keeps the file size to a minimum, so that it needn’t use much space on your hard drive. This is an important feature within CAD: complex drawings can consist of many elements, and designers and engineers will often be working on multiple projects at any one time. It is therefore helpful to keep files as small as possible, so that there is enough storage available for all of the files that you wish to view and edit.

While DXF files are not necessarily much larger than their DWG equivalents, smaller is also going to be better when transferring files to clients or colleagues. There are various ways of sharing large files, but there is usually a limit on the amount of free space the service of your choice will provide. Keeping costs down is important, particularly if you’re part of a small studio, or working freelance. And when something as simple as using a particular file format will help you keep within budget, all the better! 

5. Backwards compatibility

Details of DWG files that can be viewed with the Autocad DWG Columns for Explorer App

With DWG Columns for Explorer, you can decide what details about DXF and DWG files you wish to be displayed, including version information and revision number. Image source: Autodesk

Although you may run into difficulties trying to read the latest DWG files using old versions of AutoCAD, the reverse is not true. Since Autodesk pushes an updated version of AutoCAD out every year (you can read all about the latest update here), backwards compatibility is a very handy feature.

First off, it eliminates the need for different project members to own the same software release. Programs like AutoCAD are expensive, and agencies choose to update them at different rates. Individuals can ‘save-down’ to former versions when necessary—something that may be particularly pertinent to subscribers of AutoCAD 2018. Prior to this release, developments to drawing files had somewhat ground to a halt, with no evolution for half a decade. Now, however, DWG has progressed once more: the file format has been updated to streamline the open and save processes.

Since it’s not always clear at first glance which DWG update has been used in making a file, Autodesk have produced a useful tool that allows you to see all the information associated with it. In addition to displaying the relevant version, the DWG Columns for Explorer also shows users key data like any comments, custom properties, and revision number.

Backwards compatibility is also advantageous for companies revisiting projects from the past. This is something especially common within the construction industry, where a site may be extended as more funds become available. In this scenario, firms can safely upgrade to new software versions without affecting the readability of their architects’ files.

6. It’s all in the detail

DWG files are vector by nature—and in most applications across design industries, this helps them offer significant advantages over raster types

Raster files, like JPEGs, are represented by a grid of pixels, which are prone to distortion. The further you blow up a raster image, the more blurry it will become. This makes them unsuitable for use on a large scale.

Vector files, on the other hand, retain their quality—no matter how far you zoom in. The DWG format, as a vector file, is perfectly scalable; whether you’re looking at a 2D image, or 3D geometry, the file can be displayed at any size, without any loss of definition.

In practical terms, this is particularly helpful for the latter stages of design: up-close, the drawing stays sharp and focused, so that CAD users can play about with the details.

7. DWGs promote a real-world coordinate system

Geographic coordinates available in AutoCAD

You may choose where your in the world your project is being built, to make project collaboration easier and more effective. Image source: Autodesk

When producing plans, designers and engineers often draw to real world coordinates. The DWG format allows them to do so. This means that all designs are correctly positioned on their respective construction sites, wherever on the globe it may lie.

DWGs retain coordinate information, so that when they are imported into, or exported from, various software packages, drawings maintain their real world position. This feature extends to both two- and three-dimensional information, which can easily be exchanged between the major drafting programs, such as Vectorworks and Revit.

Keeping all files positioned to the same coordinates enables quick cross-referencing between different disciplines, leading to improved project collaboration. A DWG file containing the instructions for mapping lampposts, for instance, can be directly transferred on top of a plan of the landscape. When the drawings align, it is clear whether the lighting is positioned effectively, or whether any of the posts interfere with an unusual land mass.

The coordinates are also accurate to 1mm, allowing a high level of precision in drawing and modelling. The positioning information can be exported from the DWG file into tables. Harnessing this data is crucial to the work of engineers on the ground. Assisted by GPS machines, they can quickly and easily set out construction sites to the tight tolerances required on building projects.

The fact of the matter

The DWG format is one of the most commonly used file types within the CAD industry—and for good reason. But who could have guessed that it also possesses such a rich history? Or that it has been embroiled in a passionate controversy that spans the decades since its introduction?

Learn more in the 7 interesting facts series:

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