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Google updated its Google Image best practices to specify that images referenced in structured data must be in one of the image file formats that are supported by Google Images. These formats include BMP, GIF, JPEG, PNG, WebP, and SVG. Google supports in structured data all image formats supported by Google Images, namely the following formats: BMP, GIF, JPEG, PNG, WebP, and SVG.
As Kenichi Suzuki put it "You can now use all the image formats Google Image supports (BMP, GIF, JPEG, PNG, WebP, SVG) in Structured Data."
Gary Illyes from Google clarified it took a while to confirm which image file types were supported but they did it:
took a while to figure this out, but finally we're there! if you run into problems with images in structured data, please leave feedback through the feedback tool and either @LizziHarvey or i will look.
— Gary 鯨理／경리 Illyes (@methode) August 6, 2020
(just try to be descriptive. "it doesn't work" is not good feedback) https://t.co/5HUsshGlgp
Google's docs now say "Google Images supports images in the following formats: BMP, GIF, JPEG, PNG, WebP, and SVG."
Forum discussion at Twitter.
