Traditionally to view any Inventor files without having an Inventor license was a case of you having to download the Inventor View software. This was found on the installation media or you could download it doing a quick google search.
Recently the Internet based Autodesk Viewer was introduced. This allows you to open, amongst other CAD formats, Inventor parts, assemblies and drawings. This viewer is accessible on any internet enabled device with an Internet browser and the beauty of it is you just have to drag and drop the files onto the page and it accepts and processes.
For offline experiences I would suggest trying either the Inventor Viewer or Inventor Read Only Mode. Now if you have noticed the Inventor Viewer is not installed with the default install of Inventor. You will only see Inventor Read Only Mode. Is it gone ….Has it been replaced?? No it has not. It is now available as a separate download from the Autodesk website https://knowledge.autodesk.com/support/inventor-products/downloads/caas/downloads/content/autodesk-inventor-view-2020.html
Alternatively it will be installed when you install the Vault Client software.
So let’s take a look at the differences in the interface. Inventor Read Only has fewer tabs and the ones that are available do not allow any editing.
The exact differences are found in the table on this link https://knowledge.autodesk.com/support/inventor/troubleshooting/caas/sfdcarticles/sfdcarticles/Viewing-Inventor-2020-Data.html and with it you can see the Inventor View software has far less capability than the new Inventor Read Only Mode. I equate the Read Only mode just to be the full Inventor with access to the editing modules cutoff.
If you are using Vault and select the View in Window command then the component will be opened in Inventor Read Only Mode.