These are some best practices for making links to books or pages in HathiTrust.
Do not use the URL in the address box at the top of your browser. If HathiTrust should ever restructure their site, those links could break. Instead, get a more durable link under the “Share” link in the left navigation bar, as seen below.
Under “Share” there is an option for a “Permanent link to this item” and for “Link to this page.” Notice that the link to the item is permanent but the link to the page is not described as permanent.
Why is the page link not permanent? If the library that uploaded the item to HathiTrust should ever delete duplicate pages or add pages that had originally been missed, it will cause the link to go off by that number of pages. Automated link checkers can never detect this kind of problem, and HathiTrust is not set up to send notifications when books are reprocessed. Impermanent links must be manually checked on a regular basis, and this can be quite time-consuming.
Nevertheless, there is a way to get permanent links to pages of some books in HathiTrust.
Starting sometime around 2021, HathiTrust made some changes. Today, any page link copied from under "Share" will be permanent if the item had been digitized by Google. Check the watermark at the bottom of the page to see if Google had digitized the item.
Keep in mind that if you copied the link for a Google-digitized item several years ago, it will be the old format and will not be permanent.
It is hard to know exactly when this change went into effect, but you can tell whether your existing links are of the new, more permanent variety by looking for "Bownerid" near the end of the URL. The following two links lead to the same page in a book digitized by Google. The first one was captured several years ago and is the older variety. It is not permanent. The second one can be relied upon to always land on the page that was intended.
https://hdl.handle.net/2027/mdp.39015052095000?urlappend=%3Bseq=1401
https://hdl.handle.net/2027/mdp.39015052095000?urlappend=%3Bseq=1401%3Bownerid=13510798896381815-1665
To sum it up, the best way to ensure permanent links to pages in HathiTrust is to update any links you built before 2021, and check those captured in 2021 to see if they are the old or new type.
If you cannot link only to Google-digitized items, consider placing an annotation in your links that cite the book page number it is intended to land on. You will still have to manually check those links from time to time, but it will be quicker.
