Hydrus is described as 'A personal booru-style media tagger that can import files and tags from your hard drive and popular websites. Content can be shared with other users via user-run servers' and is a popular Imageboard in the photos & graphics category. There are more than 10 alternatives to Hydrus for a variety of platforms, including Windows, Linux, Mac, Self-Hosted and Microsoft Edge apps. The best Hydrus alternative is TagStudio, which is both free and Open Source. Other great apps like Hydrus are TagSpaces, Eagle , GCstar and Pinry.
Pinry is a self-hosted browser application whereas Hydrus is a desktop software.