Google’s John Mueller said on Reddit, ” No matter what the website is all about, Google needs textual content on-page.” This is applicable to those whose websites only contain images, videos, audio and other kinds of multimedia.
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John Mueller Reddit Statement
Google needs textual content for understanding user’s audio, video files more accurately. Google is not able to understand the content fully in those files. Although, Google is trying to get better in understanding files other than the context it would still be preferable if the textual content is present.