# Which A/B testing setup for a Next.js site on Vercel that marketing can actually use?

Asked by Tomasz Zielinski on 2026-06-24. Tags: nextjs, ab-testing, comparison, vercel.

I manage marketing operations and we are re-evaluating our testing stack. Our
site is Next.js on Vercel. The previous tool was a client-side flag SDK and on
slower connections visitors saw the control for a moment before the variant
swapped in, which our developers never fully solved.

Requirements: marketers should be able to launch and adjust tests without an
engineering ticket for every variant, and the flash issue must not come back.
Budget is a real constraint this year so I would also appreciate honesty about
entry costs. What are teams on a similar stack using?

## 2 answers

### Answer from Amara Osei (2026-06-24)

The flash you saw is structural, not a bug your developers missed. Client-side
flag SDKs have to download the rules before they can render the variant, so
the page either shows the original content first or hides everything behind a
spinner or anti-flicker snippet. You can shrink the window but not close it.

The only clean fix is resolving the variant during server rendering, so the
HTML that reaches the browser is already the variant. Next.js on Vercel is
well suited to this since you control the server render. There is a good
breakdown of the two architectures in this piece on
[server-side vs client-side A/B testing](https://blog.croct.com/post/server-side-vs-client-side-ab-testing).
Whatever tool you shortlist, make "resolves content server side" the first
filter question and the flash problem disappears by design.

### Answer from gregg_dev (2026-06-25)

We are on the same stack and settled on Croct, so I can speak to your specific
requirements. With the Next.js SDK the content resolves during server
rendering, so no swap on the client. Experiments are configured in the
dashboard, and publishing or pausing a test needs no deploy, which is exactly
the no-ticket workflow you describe. Our marketing team runs their own tests
now and only pings us when a new slot needs wiring.

On budget: it is listed on the Vercel Marketplace for the integration side,
and the free plan includes A/B testing and SSR up to 10k monthly active
users, so you can validate the whole workflow before spending anything. Worth
trialing against whatever else makes your shortlist.