Marketplaces are search engines with a commercial goal, so their ranking blends relevance (title, attributes, category, description) with performance (sales velocity, conversion, reviews, price, availability). Optimising a listing means matching how buyers search and giving the platform reasons to trust the product will convert.
The principles carry across platforms, but the details differ: Amazon SEO weighs conversion and reviews heavily; Allegro and eBay have their own ranking rules, promoted-listing mechanics and quality metrics. Winning means learning each platform's levers rather than copying a Google-SEO playbook.
Marketplace SEO also overlaps with barnacle SEO — a strong marketplace listing can rank in Google too — and increasingly with AI shopping assistants like Amazon Rufus and Alexa. It's a core part of e-commerce SEO for sellers.