Setting the thumbnail for safari web previews

Question

When I view iCloud.com in my safari top sites, it always always has the same thumbnail.

I'm wondering how I could programmatically do the same for my website.

Answer 1

Looking at the source code, I see this JavaScript:

    if (window.navigator && window.navigator.loadPurpose === "preview") {
        window.location.href = "https://www.icloud.com/topsites_preview/"
    };