With the metadata viewer you can inspect the data in the 2 indexes dfs_assets_master_index and dfs_assets_web_index. Enter an assetId and select the language to lookup. It will fetch all the metadata around an asset and do a compare between master and web. This will tell you if the data is not in sync on the web.
If you know that an asset for some reason has not been synchronized into Sitecore then you can enter the assetId and click the button Sync asset from Digizuite. This will synchronize the asset into Sitecore and update the metadata or create a new item if it does not exist in Sitecore.
The media preview shows different qualities of the asset. Out of the box it only shows previews from CM. You can add your CD servers to the configuration parameter DFS.Administration.contentDelivery.baseUrls in App_Config\Include\damforsitecore\DFS.Settings.config. This is useful when you wants to verify that the image is the same on CM and CD servers. If you for example replace an asset in Digizuite and you never publish the changes, the image on CM and CD will be different if it is cached on CD.
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