A shopper looking for a navy fleece opens Google Images before they open a single store, because they want to see it before they read about it. Your photo is either in that grid or it isn't. Text the shopper never reads, mostly around the photo, makes that call.
Product images earn their place in three ways. They load fast, they describe what they show, and they're the one image your structured data points Google to.
Google reads the text around a photo
Google's Images best practices document says where its understanding of an image comes from: the filename, the alt attribute, any caption, the text near the image, and structured data. It leans on what you write around the photo. That's why the same supplier photo can rank on one store and never appear for another.
Three places carry that meaning:
- The filename. Google's own example prefers
my-new-black-kitten.jpgtoIMG00023.JPG. For a store, that meansridgeline-3-trail-shoe-navy.jpgrather than a camera export code. Rename before upload, because most platforms keep whatever name arrives. - The alt text, covered in the next section.
- The surrounding text. Google says to place images near relevant text, on pages relevant to the image's subject. A product photo beside the product's name and description does exactly that. The same photo in a homepage slider with no caption doesn't.
Write alt text for the shopper who can't see the photo
Alt text exists for people using screen readers and for browsers that fail to load an image. Google reads the same attribute. Write it for the first audience and the second is served.
Describe what the image shows, in a buyer's words, specific to that image. Google warns against stuffing the attribute with repeated keywords. Its bad example lists "puppy dog baby dog pup" and so on, while its good example describes the scene. For a trail shoe, the main shot gets "Ridgeline 3 trail running shoe in navy, side view". The detail shot gets "Ridgeline 3 outsole showing the lugs and heel". The lifestyle shot gets "Runner wearing Ridgeline 3 shoes on a muddy trail".
A few rules make this quick:
- Give every image on the page its own alt, not the product name repeated.
- Name the variant in variant images, so the navy photo and the red photo read differently.
- Give decorative icons an empty alt attribute so screen readers skip them.
- Leave out "image of" and "photo of". The screen reader already announces that.
Your platform's image editor has an alt field for each image. Many themes fall back to the product title when it's blank, which is why every photo on most stores ends up saying the same thing.
The main image decides your load time
The largest thing in the first screen of a product page is almost always the main product photo. Core Web Vitals measure that element as Largest Contentful Paint. web.dev's thresholds call a Largest Contentful Paint of 2.5 seconds or under good, measured at the 75th percentile of visits, and Google's page experience documentation says its ranking systems use Core Web Vitals. Serve a camera-sized photo at full size to a phone and you fail the measure on every product page at once.
Four habits fix most of it:
- Upload images at a sensible size and let the platform generate the display sizes. Google's image guidance recommends responsive images, where the browser picks a smaller file for a phone. Modern themes do this; older ones serve one file to everything.
- Serve modern formats such as WebP or AVIF where the platform supports them. The image services built into the major platforms convert automatically.
- Lazy-load images below the first screen, but never the main product image. Deferring the hero delays the exact element the metric measures.
- Keep the zoom image as a separate larger file that loads only when the shopper zooms.
Store speed and themes covers how to measure this, and Core Web Vitals explained covers the metrics themselves.
Getting into image and shopping results
Google's Images guidance says structured data can make your images eligible for enhanced results. Its merchant listing documentation makes an image a required property of Product markup. Google shows that image beside your price, so it has to be the product.
The same documentation recommends several high-resolution images per product, each at least fifty thousand pixels when width is multiplied by height, in 16:9, 4:3 or 1:1 aspect ratios. It also requires the image to represent the product being marked up. Put a logo or a placeholder in that field and you forfeit the feature.
Two more things help the photos get found. Google recommends an image sitemap, which is useful when your images live on a CDN domain. And the crawler has to be able to fetch the file, so an image host blocked in robots.txt can't be indexed.
Frequently asked questions
What is an image alt text example?
For a trail shoe, the main photo might get "Ridgeline 3 trail running shoe in navy, side view". A close-up of the sole gets its own line, such as "Ridgeline 3 outsole showing the lugs and heel". Each one says what that specific image shows, with the variant named.
Is image alt text important for SEO?
Yes. Google lists the alt attribute among the sources it uses to understand an image, next to the filename, nearby text and structured data. Descriptive alt text can help a product photo surface in image results. Stuffing it with repeated keywords works against you, because Google's guidance calls that out as a bad example.
What is the purpose of alt text?
It gives people who use screen readers a description of the image, and it shows in place of the picture when the file fails to load. Google reads the same attribute. Write it for the shopper who can't see the photo and search benefits follow.
How can I tell if an image has alt text?
Right-click the image, choose Inspect, and look for the alt attribute on the highlighted img tag. If it's missing, empty on a product photo, or the same product title repeated on every image, it needs work. Your platform's image editor also has an alt field for each image.
What to take away
- Google understands a product photo from its filename, alt text, nearby text and structured data, so the same photo can rank on one store and not on another.
- Alt text describes what each image shows for a shopper who can't see it, one description per image, with no repeated keywords.
- The main product image is usually the Largest Contentful Paint element. Size it for the screen, serve a modern format, and never lazy-load it.
- Product markup requires an image, and Google recommends several high-resolution photos per product that show the product being marked up.
Next
One product, six colours, four sizes: now decide how many pages that should be. Continue with Variants and duplicate content.