Reference
What is Image SEO?
Image SEO covers two jobs at once: making images discoverable, and stopping them from slowing the page down. That means descriptive filenames, meaningful alt text, modern formats such as AVIF and WebP, correct sizing for each viewport, and an image sitemap where images are genuinely a discovery channel.
Also called: image optimisation · image search
Discoverability
- Descriptive filenames — oak-sliding-wardrobe.jpg rather than IMG_4471.jpg
- Alt text written for a person who cannot see it, which produces the best version for search too
- A caption and surrounding text, both of which inform what the image is understood to show
- An image sitemap where images matter — product photography, portfolios, galleries
Performance
- AVIF with a WebP fallback and a JPEG or PNG last
- Several widths with srcset and sizes, which saves more than any format choice
- Width and height declared so nothing shifts
- Lazy-load below the fold, never the LCP image
The one image most people ignore
The Open Graph card is the image most people actually see, because it appears every time the URL is shared. One generic card for a whole site means a pricing page and a case study preview identically.
Where this is covered in depth
A definition can only go so far. Image SEO: findable images that do not wreck your page speed covers this properly — 3 minutes, free, no email required.
Who wrote this
Anas Bin Masud builds e-commerce sites and does technical SEO for businesses in the UK, Canada and Pakistan. These definitions come from client work rather than from a content brief — where an entry describes a mistake, it is usually one found on a real site. More about how I work.