Definition
Image SEO is the set of practices that help search engines understand images and that let those images earn traffic through image search and enrich the pages they sit on. It covers descriptive file names, accurate alt text, relevant surrounding text and captions, appropriate dimensions and modern compressed formats, responsive delivery, lazy loading done in a crawlable way, an image sitemap or proper markup for important images, and structured data where an image supports a rich result.
The two goals are discoverability and performance. Well-described images can rank in image search and appear in rich results, and images are often a meaningful traffic source for visual topics.
At the same time images are usually the heaviest part of a page, so optimising their size and loading directly improves Core Web Vitals and the page-experience signals that affect ranking.
In context
For an iGaming affiliate, image SEO is mostly about performance and accessibility rather than image-search traffic, because gambling imagery does not attract much image search and Google is cautious about surfacing it. The high-value work is compressing and correctly sizing the screenshots, logos, comparison graphics and diagrams that fill review and glossary pages, serving them in modern formats, and loading below-the-fold images lazily so the initial render is fast on a mid-range phone.
This is one of the most reliable ways to improve Core Web Vitals on a content-heavy site.
Alt text matters for accessibility and as honest on-page context: describe what the image actually shows (a screenshot of a cashier page, a diagram of a funnel) rather than stuffing keywords. Keyword-stuffed alt text is both an accessibility failure and a spam signal.
For screenshots used as evidence in reviews (payout times, bonus terms, KYC steps), clear captions and surrounding text explaining what the image demonstrates also support the first-hand-experience signals that help this kind of content. Structured data and image sitemaps are worth it only for images that genuinely support a rich result.
The practical priority order for this sector is: page speed from image weight first, accessibility and honest context second, image-search discoverability a distant third.
Worked example
An affiliate audits a slow review template and finds uncompressed PNG screenshots are 70% of page weight. It converts them to compressed modern formats at display size, adds descriptive alt text and captions explaining what each screenshot proves, and lazy-loads below-the-fold images.
Largest Contentful Paint on mobile drops below 2.5 seconds and the page-experience signal improves.
Related terms
Frequently asked questions
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