The version of an image is the timestamp of uploading the image (e.g., v1366687335). It is required for building URLs of the latest uploaded version of an image in case that multiple images were uploaded sharing the same public ID (overwriting a previously uploaded image). It allows bypassing a previously cached version of the image.
Each image (public ID) has only the latest uploaded version available for delivery and transformation. The version value is included in the response of our upload API call.
Here's a sample URL with the version component:
Cloudinary's does not require the version component to be present in URLs (but you might get a previously cached version in this case). For example: