Yesterday Anna was asking about image alt text and I realized that I haven't written much about it before:
I have a lot of pictures on my site, and Shopify makes it easy to add an alt tag to each image. I always get confused though. How many words is best, should I always add my Brand name, do I describe the picture or just describe the product as much as possible?
Basically you want to describe the image.
That's the most accessible option and the most future-proof for SEO (plus there are stores getting sued for being inaccessible. It seems like opportunistic lawsuits but they could become more commonplace soon).
One way to think about it is, whatever you use for the alt tag will be read out loud to a visually impaired customer (including Google's software).
So "white fountain pen writing on paper" or "examples of ink flow" would be good when selling a pen. Even a simple "side of Product Name" is okay.
SEO-wise, that text gets feed into Google's algorithm just like text content on a page. It helps the most in Google Image Search but even the regular Search benefits from good alt text.
One of Shopify's engineers on accessibility also wrote about what content to put into alt tags. Though it's probably more in-depth than what most stores need, especially if you have a large number of images.
But some basic alt text is better than no alt text or any computer generated alt text.
That's just one of the reasons why it's trusted by thousands of Shopify stores.