How can I make the popover panel full width in Header?

[tasnimultas67]

How can I make the popover panel full-width in the Header? I'm making a mega menu. It doesn't work even after I put the w-full CSS class on the popover panel.

[manimovassagh]

The PopoverPanel is positioned relative to its PopoverButton by default (via Floating UI), so w-full just makes it as wide as its own content container, not the full viewport.

For a mega-menu style full-width panel, you need to break it out of the button's positioning context. Here is how:

Approach: Use a wrapper with relative positioning on the full-width container

Wrap your entire header nav in a relative container, then position the panel absolutely within that:

<div className="relative"> {/* full-width header container */}
  <nav className="flex items-center justify-between px-6 py-4">
    <Popover>
      <PopoverButton>Products</PopoverButton>
      <PopoverPanel
        anchor="bottom start"
        className="absolute left-0 right-0 w-full z-50 bg-white shadow-lg"
        style={{ position: "fixed", left: 0, right: 0, width: "100vw" }}
      >
        <div className="mx-auto max-w-7xl px-6 py-8">
          {/* mega menu content */}
        </div>
      </PopoverPanel>
    </Popover>
  </nav>
</div>

Alternatively, use portal to render the panel at the root of the DOM, then apply fixed positioning yourself:

<PopoverPanel portal className="fixed inset-x-0 top-[64px] z-50 bg-white shadow-lg">
  <div className="mx-auto max-w-7xl px-6 py-8">
    {/* mega menu content */}
  </div>
</PopoverPanel>

Replace top-[64px] with whatever your header height is. The portal prop ensures the panel is not constrained by any parent overflow or positioning context.

The portal approach is generally the cleanest for mega menus since you have full control over placement.