Soft 404 is a page that appears to be missing or unhelpful but returns a success status instead of a proper not-found status.
It matters because technical issues can prevent great content from being discovered, rendered, indexed, or trusted. Strong technical foundations protect rankings during redesigns, migrations, content expansion, and platform changes.
Example
A removed product page returns 200 but displays only ‘Product not found’. A search engine may treat this as a soft 404 because the content signals a missing page even though the HTTP response claims success.