What if there are more images than one on the page? Then you'd have images with same alts. I don't think this would do negative impact on SEO, but alt text is really not for that. They are meant primarily for visually disabled people, and doing this would make a bad impact on their UX. Not that they are not used to it though. unfortunately. I understand the work involved to alter all that, but perhaps you could at least set some priorities. You could check the top ranked images, and also evaluate the ones that could be more important, and provide them with manual alt text? Bonus tip: end each alt text with a period. (. ) A period at the end makes the screen reader pronounce it nicer.
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