To update metadata for a video, you first need to provide information to identify the video you want to update. You use the YouTube-assigned video ID to uniquely identify the video. The XML snippet updates the title of the video without affecting its other metadata:

    <video type="episode" id="VIDEO_ID_1_">
      <title>New video title
    

You only need to provide values for the metadata fields you are updating. The new values overwrite the previous values, even for fields like <keyword> that accept repeating values. You cannot incrementally update a repeating tag value by only adding the new values in your feed.

If you leave a field out, it will not be updated, and fields that have default values will not be reset to their defaults if you omit them. Or, if you prefer, you can provide all of the metadata for the asset in the update request, specifying the already existing values for fields that have not changed.

When you upload a show or movie to YouTube using the XML content feed, you can specify values for certain metadata fields as part of the asset definition or the video definition. For example, you can identify the <director> as a subtag of the <asset> tag or the <video> tag. When YouTube processes your upload, these shared metadata tags are ultimately stored as part of the video regardless of where you specified them in the feed.

If you subsequently need to update the values for these fields, you must update the video, not the asset. You need the video ID, not the asset ID. You won't receive an error if you update the asset, but your changes won't be reflected on the video.

* Nguồn: Youtube