I've been helping a team with their free wallpaper gallery - think desktop backgrounds, live wallpapers, that sort of thing. Before the March 2026 core update we'd built up about fifteen thousand indexed pages. Within ten days, that number collapsed to just six. most URLs now show up as 'Crawled - currently not indexed' in Search Console. no manual actions, no security warnings, nothing obvious in GSC.
At first it seemed like a brutal, indiscriminate drop. But after digging into the site structure, something stood out. Someone with a sharp eye pointed out that the HTML lacks semantic elements like <article> and <nav>, yet uses <main>. That tag is supposed to hold unique page content - but on each page, the 'You may also like' section sits inside it. With twenty-four related items per page, well over half the visible content is essentially duplicate across the entire site. add to that a missing robots meta tag - no explicit crawl directives - and you've got a recipe for the crawler to waste its limited budget on near-identical material.
From a brand strategy perspective, this is a classic case of search engines re-evaluating perceived quality at the template level. When every page feels like a slightly different wrapper around the same core content, the entire site gets labelled as thin. The brand signal becomes 'we don't offer distinct value page by page'. That's exactly the kind of pattern a core update would hammer.
No bought links, no spam - just a structural blind spot that undermined the positioning of every single URL. Fixing the semantic layout and shifting the duplicate widgets outside <main> might help, but it's a painful reminder that technical structure is brand infrastructure.
