Google Image Search sends a lot of ecommerce traffic, especially in visual categories like fashion, home décor, and handmade goods. If your product images don't have alt text, Google can't index them. They're effectively invisible.
Image SEO is one of those areas where a small amount of effort pays off well. Most stores have hundreds of product images with missing or generic alt text, oversized file sizes, and meaningless file names. Fixing them opens up a traffic channel that most competitors ignore.
Why alt text matters more than you think
Alt text (alternative text) serves three purposes:
- Search engine indexing: Google can't "see" images the way humans do. Alt text tells search engines what an image shows, which determines whether it appears in Google Image Search results.
- Accessibility: Screen readers use alt text to describe images to visually impaired users. Good alt text is a legal requirement in many jurisdictions under accessibility regulations.
- Fallback display: When images fail to load (slow connections, broken URLs), alt text appears in place of the image so users still understand what was there.
For eCommerce stores specifically, Google Image Search is a direct traffic source. A shopper searching for "blue linen midi dress" might click on an image result and land directly on your product page. But only if your image has alt text that includes those terms.
What good alt text looks like
Good alt text is descriptive, specific, and natural. It describes the product as if you were explaining it to someone who can't see it.
- Bad: "product image" or "IMG_4832.jpg" or empty (""), which tells Google nothing
- Okay: "blue dress". Too generic to rank for anything specific.
- Good: "Blue linen midi dress with puff sleeves, front view". Descriptive and keyword-rich without being spammy.
- Best: "Women's blue linen midi dress with puff sleeves, available in sizes XS to XL". Includes product attributes that match how shoppers search.
A good rule of thumb: describe the product as you would to a friend over the phone. Include the product type, colour, material, and any distinguishing feature. Keep it under 125 characters.
The file name and format matter too
File names
Rename your image files before uploading. Search engines use file names as a secondary signal for what the image contains. blue-linen-midi-dress-front.webp is more useful than DSC00847.jpg. Use hyphens to separate words, keep names lowercase, and include the primary keyword.
Image format
WebP is currently the best format for web images. It offers 25-35% smaller files than JPEG at the same visual quality, and it's supported by all modern browsers. If your platform doesn't support WebP, use JPEG for photos and PNG only when you need transparency.
File size
Large images are the single biggest cause of slow eCommerce page loads. Aim for under 200KB per product image. Most product photos can be compressed to 80-150KB without any visible quality difference. Use tools like Squoosh, TinyPNG, or your platform's built-in image optimiser.
How image issues compound across your store
If you have 500 products with 3 images each, that's 1,500 images. If even half are missing alt text, that's 750 images invisible to Google Image Search. If those images average 500KB instead of 150KB, your pages are loading 2-3 seconds slower than they could be.
The compounding effect is significant: slower pages hurt rankings for all keywords (not just image search), missing alt text locks you out of an entire traffic channel, and poor image SEO signals to Google that your site lacks attention to detail.
Auditing your store's image SEO
Manually checking alt text across hundreds of product images isn't practical. You need an automated scan that flags every image with missing or generic alt text, identifies oversized files, and prioritises fixes by impact.
RankCart's Image SEO tab (Starter plan and above) covers the alt text part for the page you audit. It lists each image on that page with missing alt text and gives a suggested alt text, generated from the product context, for you to review. It does not measure image file sizes; the image opportunities in PageSpeed Insights cover that.
Quick wins you can do today
- Pick your top 10 selling products and check their alt text right now. If any are empty or generic, rewrite them with descriptive, keyword-rich text.
- Check your homepage hero image. It's often the largest file on your site and a common source of slow LCP scores.
- If you're adding new products, set a standard: every image gets proper alt text, a descriptive file name, and WebP format before it's uploaded.
- Run a free RankCart audit to see how many images on a page are missing alt text, how fast that page loads, and the estimated revenue at stake.
