Image Delivery Service Known Issues

Slow or Degraded Image Performance in Harvard Digital Collections

• When users experience slow loading or broken images in HOLLIS, HOLLIS Images, Harvard Digital Collections, or CURIOSity, there are a few factors that may be contributing to the issue.

  1. Some of the image delivery technologies used by the Libraries have degraded in their ability to reliably serve images.
  2. Many older images in our collections have invalid metadata that are incompatible with newer generations of imaging standards and software.
  
  

  To address these problems, the Library Technology Services has several projects underway:

  • We have rebuilt and updated our image delivery systems to support the latest versions of IIIF and use a modern, well-maintained image server.  In order to take advantage of the new systems, we are in the process of migrating over 42 million images to the new environment. This migration is expected to be complete in the first quarter of next year.
  
  
  • We are upgrading our image viewer software from Mirador 2 to the newer Mirador 3. A beta of Mirador 3 is available now but the full transition depends on the image migration.
  
  
  • A project is identifying images with invalid or incompatible metadata so they can be remediated or regenerated to load properly.
  
  

  We have recently made a change that displays a placeholder image instead of images that we have determined to have invalid header data and may not load correctly.  The placeholder image looks like this:

In summary, occasional slow loads or error messages like the above may be experienced until the migration is finished and outdated images are addressed. Library Technology Services is working actively to complete these upgrades and resolve issues to improve the digital experience.