Welcome Mat
A full-screen overlay shown on page load that presents one offer before the visitor sees any of the page content.
A welcome mat is a full-viewport popup shown immediately on arrival. Unlike a centered modal, it occupies the whole screen and either scrolls away or slides up to reveal the page beneath. The visitor sees the offer first and the content second.
That order is the problem. Google Search Central's guidance on intrusive interstitials specifically describes a popup that covers the main content immediately after a user arrives from search on mobile as a pattern that can affect rankings, and a welcome mat is exactly that pattern. It also asks for an email from someone who has no context yet, the weakest possible moment for the request.
Where a welcome mat still makes sense is on pages visitors reach with intent already formed: a landing page from a paid ad, a launch announcement, or a returning-visitor segment that already knows the brand. On organic entry pages, a scroll-triggered or exit-intent popup delivers the same offer at a lower cost in goodwill.
See it in practice