We make a best-effort to create thumbnail previews for a better user experience, but sometimes cannot due to irregularities in the file or when it exceeds certain limits. Our success rate exceeds 99% and we are continually researching and improving our thumbnail generation abilities.

Why a thumbnail preview might be missing

• Unsupported File-Type
  While we try to generate a preview for as many file-types as possible, we aren't able to support 100% of file-types. Check out this article for a list of supported file types. 

• File extension doesn't match the file-type
  Sometimes the extension in the filename makes the files appears to be a certain file-type, but the file is actually be a different file-type. This can happen if the filename is changed manually after it's saved.
  Example: The filename is "filename.pdf" but the file is actually a Microsoft Word doc.  

• Corrupted File
  Sometimes irregularities during file usage/export/download can cause a file to become corrupted. When this happens, it's possible that an image will not preview. 

• File too large                                                                                                            While Image Relay can store files of any size, we cannot render previews for files over a certain limit. Visit this article on file types and sizes to see the preview size limitations.  

Missing a thumbnail preview? Try this:

• Retry the upload
  Sometimes re-uploading the asset will solve the problem, similar to the old turning off the computer and turning it back on trick. You may want to delete the first attempt so that you do not have duplicates in the system.  

• Replace Thumbnail feature
  If your file is missing a thumbnail preview and you'd like a visual reference, instead of the thumbnail icon, here's how you can replace the thumbnail with an image of your choice.

If you are having continued issues with your thumbnail previews, please contact support@imagerelay.com.

Further Resources:
Upload to Image Relay
The Image Relay Glossary