Slow Explorer Progress Bar On Large Folder

Clicking on a large folder in Explorer can cause a slowly-moving green progress bar. In some cases this can take several minutes to complete.

A common cause is thumbnail caching of image and video files, resulting from having properties | customize | "optimize this folder for:" set to pictures, vs documents or General items.

The most likely solution: in Explorer, right click on folder, select properties, customize, under "optimize this folder for:", select either General items, or documents. Set check box "Also apply this template to all subfolders", then click apply.

The slow progress bar is apparently caused by Explorer scanning the folder and all subfolders to pre-render thumbnail images for image and video files. This happens if the "optimize this folder" setting is pictures or videos. This happens when merely clicking on the top-level folder.

If "optimize this folder" is set to documents or General, the thumnails are not rendered until you actually click on the folder or sub-folder containing those.

This was discussed in another thread on this forum, but it was full of speculative remedies, and the actual cause and remedy was not posted until the last thread (and one year after the thread was started): Accessing drives in Windows Explorer takes a long time I'm creating this thread with a more exact title and concise description, to aid in finding the solution based on a symptom search.

While the above is the most likely cause of a slow Explorer progress bar, there are other possible causes. These include clicking on a remote folder on a slow network, general slowdown due to indexing, disk drive or filesystem caching disabled, disk drive retries due to impending hardware failure, corrupted video files or codec, etc.