My Next.js articles shipped inside a hidden div, and nothing warned me

dev.to WebDev2026-11-07 16:590 views

My pages looked fine in a browser. Google was indexing them. Then I read the HTML the way a crawler reads it, with no JavaScript:

curl -s https://your-site.com/some-page -A 'OAI-SearchBot/1.0'

There was a header, an empty slot and a footer. The article came after the footer, inside <div hidden id="S:1">. A small inline script moves it into the slot when the page loads.

Googlebot runs that script. A crawler that doesn't run JavaScript gets a hidden block at the bottom of the page. I can't see inside every crawler to know what it does with that. I didn't want to bet my pages on it.

The cause

One wrapper I had written on purpose:

<Suspense fallback={null}> <Content params={params} /> </Suspense>

I assumed a boundary that finishes at build time gets inlined. Not always. React has an option called progressiveChunkSize, 12,800 bytes by default. A boundary bigger than that gets outlined: the slot goes out first, the content later. The rule is about size, not about waiting.

You can prove it with nothing async at all. I rendered a plain Suspense boundary with React 19.3's renderToPipeableStream:

Boundary size	Article hidden after the footer?
2,000 bytes	No
12,000 bytes	No
14,000 bytes	Yes
40,000 bytes	Yes
40,000 bytes, with `progressiveChunkSize` raised	No

The limit counts HTML bytes, not words. Tailwind classes count. Even my shortest page, a list of five calculators, crossed it.

How to check

Find your <h1> in the raw HTML. If <div hidden id="S: comes right before it, you have this.

The fix

Stop wrapping the article. With Cache Components on, reading params outside Suspense fails the instant navigation check, so routes with a dynamic param also need:

export const instant = false;

That turns off a check, not prerendering. My pages still answer x-nextjs-prerender: 1.

Most of my fallbacks were null, so I lost nothing there. A blank page was never instant in any way a person would value. On my docs I did give up a loading skeleton. I took that trade.