Beyond being a nice thing to do, offering your 3D models to the Sketchfab community as a free download has benefits:
You can earn additional upload credits in a month by making some of your existing models downloadable (and public). See Upload Limits for details.
Public downloadable models are exempt from being disabled. (Private downloadable models are not.)
How to make your model downloadable:
Go to your model page and click Edit Properties.
Find the Download setting and change it from No -> Free (or Store if you are an approved seller).
Choose a license type for your model.
Click Save Changes.
Note: You can only turn off downloads if you have remaining upload credits on your account.
If you've applied and been accepted to sell in the Sketchfab Store, you can change your Download status from No/Free -> Store.
Licenses
When you make your model free to download, you'll need to choose between a Standard License or a Creative Commons license to place it under:
Standard License - you may use the 3D asset worldwide, in all types of media, for all types of use (whether commercial or non-commercial), in all types of derivative works. Others can do the same, as none of our licenses are exclusive.
CC BY - Attribution: depending on the NC, ND, and SA choices, others may share, edit, and use the model, but they must give you credit for the original work.
CC BY-NC - Non Commercial: others cannot use your model commercially
CC BY-ND - No Derivatives: others may use and share the model, but it cannot be altered.
CC BY-SA - ShareAlike: depending on the NC choices, others may share, edit, and use the model, but derivative work must be shared under the same license.
No Derivatives and ShareAlike are mutually exclusive.
You can change the license at any time from the model page. For more details or to report a problem, see Report Violation.
For information on the licenses available for non-free Store models, see Licenses.
Unable to make your models downloadable
Certain software companies do not allow models made with their tools to be available for free download.
If you've used an exporter to upload your model to Sketchfab from one of the following software options, you won't see the Download option available on the model page:
Cappasity Easy 3D Scan
Reallusion Character Creator 2
itSeez3D (free version)
Keyplan 3D
Qlone (free version)
Qubicle (Basic version)
Skanect