Skip to main content Skip to secondary navigation

SDR Metrics

Main content start

Learn about how we generate usage metrics.

We track and display views of SDR objects, either embedded on PURL pages or elsewhere, and how many times the files for these objects are downloaded. We aggregate views and downloads from users into a single visit, or session, to prevent overcounting. We also track the unique identifier of the object being viewed or downloaded and where the view or download originated (also known as the Referrer), e.g. the page embedding the object.

How do you define a view?

A view is defined as a distinct user (human or machine) loading an embedded SDR object during a one-hour time period. If a specific user loads the embedded object more than once during this hour, it is still counted as just one view.

Our embed viewer generates an HTML frame when an object is embedded in a page. We count loading of that frame as a view, regardless of whether it's embedded on a Stanford-owned website or externally.

How do you define a download?

A download is defined as a distinct user (human or machine) downloading one or more files from an SDR object during a one-hour time period. If a user downloads multiple individual files and/or a zip file containing all the files on the object during this hour, it is still counted as just one download.

We count downloads of the files from their location in our digital stacks, no matter where these downloads originate. This means we can track downloads that are initiated by clicking a link in our embed viewer, as well as those initiated directly via a URL, e.g. a link embedded in source code.

How often are metrics updated?

Metrics are collected in real-time. Refreshing a PURL page will display the most up-to-date metrics available.

What about robots?

Views or downloads originating from robots – for example, Google's web search crawler – are not collected. This functionality is provided by Ahoy, our metrics collection software.

Can I opt-out of usage metrics tracking?

No; usage tracking is automatic.

When did metrics collection start?

We started collecting views on Nov 20, 2023 and downloads on Dec 18, 2023. We are unable to report view and download events that happened prior to these dates. For this reason, items  already existing when data collection started may have reported values that do not reflect all actual view or download events for the item. 

What if the item has multiple versions?

The views and downloads numbers you see on the PURL pages include views and downloads for all versions of the item. In other words, if an item has been modified several times, what we are showing you is the total number of views or downloads for all the different versions of the item.

What information do you store about visitors?

We collect the standard information that all browsers automatically send with every web request:  browser, operating system, and IP address (which we anonymize).