Google changed how it handles soft 404 detection and classifications, John Mueller, a Google Search Relations Advocate, confirmed this morning. The search company now looks at each page by device type and potentially can assign the soft 404 classifications differently across the same URL on mobile versus desktop.
What are soft 404s? A soft 404 is when a page returns an HTTP status code of 200, which says the page is okay and all is good. But in reality, the page does not really load content or it cannot be found and should likely return a 404 status instead. When this happens, Google will flag those pages as soft 404s and treat the URL as a real 404 and not index the page.
