The version of an image is the timestamp of when the image was last updated (e.g., v1366687335). It is used when building URLs to ensure that the latest version of an image is requested, in case the image was recently overwritten and the old version is stored in a CDN or browser cache. By using versions in your delivery URLs it ensures that your application's users are always requesting the newest copy of the asset.
Each asset (public ID) has only the latest uploaded version available for delivery and transformation, and the version number you should use in your URLs is included in the response of our upload API calls and in our Media Library.
Here's a sample URL with the version component:
Cloudinary does not require the version component to be present in URLs, and it can be removed if you don't want to use that when building your URLs.
If you do use versions in your URLs, it's important to keep the version that you add to your URLs up to date with the asset's current version if you overwrite it; otherwise you may encounter incorrect caching behaviour in CDNs, proxy servers, or a user's device or browser cache
For more information: