Images on a page have a dual role worth exploiting: they describe what is in the image to screen readers and the search engine (through alt text), and with optimisation (format, size) they speed up page loading. Well-managed images thus improve accessibility, bring traffic from image search, and support speed.
Alt text: accessibility and SEO
Alt text (alternative text) is a description of the image that screen readers and the search engine read. It tells visually impaired users what is in the image, and helps the search engine understand the image and show it in image search - an additional source of traffic for a store.
Images as a traffic source (Google Images and Lens)
Image search is not a side matter: Google Images accounts for roughly a quarter of all searches, and visual search through Google Lens (now built into shopping) is growing, with a large share of those queries having clear purchase intent. For a store this is a valuable channel: a visitor who finds your image in image search and clicks has already seen the product and is closer to buying than a typical search visitor. A well-optimised image (clear alt text, descriptive file name, large and fast enough) therefore has a real chance of bringing customers straight to the product page.
How to write good alt text
- Concise and descriptive: usually up to about 125 characters; describe what is in the image and how it relates to the page content.
- No "image of..." at the start: the screen reader already announces that it is an image, so do not start with "image" or "photo".
- Keyword naturally: include a relevant keyword (product name, colour, material), but without stuffing.
- Decorative images: if an image conveys nothing (purely decorative), give it empty alt text (alt="") so the screen reader skips it.
An example for a product: instead of "image", prefer "Black canvas sneaker with white sole, side profile".
File names
Image file names should be short and descriptive: black-canvas-sneaker.jpg is better than IMG00023.JPG. This too helps the search engine understand the content of the image.
Format and speed
Large images slow down the page, which hurts the experience and indirectly SEO (speed is a factor). So compress images and use modern formats such as WebP or AVIF, which take up significantly less at high quality. Also add lazy loading, so images lower on the page load only when the visitor reaches them.
How to handle it in Magento
Set the alt text for each product image in the media gallery, and similarly for the category image. With a large catalog, writing by hand is not feasible - then use a dedicated SEO module to create a pattern that automatically builds the alt text from product attributes (name, category, brand) and adds it in bulk to all images. For modern formats (WebP), automatic compression on upload, and lazy loading, an image-optimisation module is usually required, since core Magento does not fully offer this.
How to measure whether it works
In Google Search Console, in the performance report, check the images tab (Google Images) - it shows how much traffic comes from image search. With a crawler find images without alt text and fill them in. Track the speed and weight of images with a speed-measurement tool (e.g. PageSpeed).
