From the documentation of the reports.query
endpoint of the YouTube Analytics API, assuming this is the endpoint you are referring to:
The API supports the ability to specify multiple values for the video, playlist, and channel filters. To do so, specify a separated list of the video, playlist, or channel IDs for which the API response should be filtered. For example, a filters parameter value of video==pd1FJh59zxQ,Zhawgd0REhA;country==IT restricts the result set to include data for the given videos in Italy. The parameter value can specify up to 200 IDs.
In other words: only use commas between video IDs (not semicolons), don't repeat the video
keyword for each ID and use ==
instead of =
.