Experience with next/root-params / rootParams

[amannn]

With rootParams being available in the latest canary release of Next.js, I'd be curious how this feature is working for users of next-intl that have already decided to give it a shot!

My impression so far has been positive, these are my findings.

Bugs/missing:

• Client-side navigations within a given segment value will return undefined for the root param value if you have multiple root layouts (ref) Fixed in Next.js 15.2!
• I couldn't get global 404 pages to work (ref) → Should be fixed by [not-found] Add global-not-found convention vercel/next.js#78783 (comment)
• rootParams return an empty object in Route Handlers (fixed in feat: handle rootParams in routes (finish changes) vercel/next.js#81086)
• Not strictly an issue with rootParams, but dynamicParams = false might not trigger a 404 in production if you're using dynamic APIs on the page (generateStaticParams with dynamicParams false does not show not-found page on production vercel/next.js#54270)

Nice-to-have:

• Switching between root layouts causes a hard refresh (I think this is working as-designed)

Let me know if rootParams works well for your app!

Update: It seems like rootParams is renamed to next/root-params.

[sannajammeh]

This API does not work for me currently in 15 latest canary. It simply returns {} for every page its called in

[amannn]

Do you by chance have a layout at app/layout.tsx? If so, that would cause the empty object. You need to make sure that you only have layouts in nested folders like [locale].

[nevnein]

FYI this has been moved from unstable_rootParams to its own package(?), see https://github.com/vercel/next.js/releases/tag/v15.4.2-canary.42 and vercel/next.js#82582

[amannn]

Yep, unstable_rootParams will be replaced by next/root-params.

It's pretty much an equivalent for the previous API with one minor difference: Server Actions are (currently) not supported. AFAIK this is still under consideration and may change.

With Next.js 15.5, a deprecation notice for unstable_rootParams was added, but the API will continue to work until Next.js 16.

[GrahamQuan]

on next 15.5.0, current api can await a value, but any type

import { locale } from 'next/root-params';

const localeValue = await locale(); // `localeValue` type is any

i wonder how to add types in the future, locale() should be Promise<'en' | 'es' | ...>

[amannn]

I think it's coming: vercel/next.js#80618

[jokull]

We just shipped triptojapan.com with root params. The code cleanup is great and we are finally using generateStaticParams.

The only issue we ran into was in preview environments. In generateStaticParams we early returned an empty array, in combination with export const dynamicParams = true; to clamp down build times in preview environments. This resulted in errors for all routes with generateStaticParams, only preview envs but not in dev. Adding just a single prebuilt route with slice(0, 1) made it work.

[amannn]

Nice! 💯

This resulted in errors for all routes with generateStaticParams

That's odd! Thanks for sharing your workaround though!

[sannajammeh]

We also shipped https://nordicdownhillseries.com with root params. Works excellent!