On September 13, 2021, as part of an upcoming Google security update, some Google Drive links (created prior to 2017) will change.
To make file sharing more secure, an upcoming security update changes the URLs for some Google Drive files and folders. The new links include a resource key in a file’s URL. To access an item using the link, users need the updated URL that has the resource key.
What Does This Mean For Me?
If you have shared links to files in Google Drive, but they're currently existing someplace outside of Google Drive (ie. a link on a another website, a link you recently shared with someone, etc) you'll want to update these links after September 13, 2021.