How to config i18n in nuxt/content v3 like defaultLocale

[NekoWings]

I found that there is not defaultLocale or any i18n config on nuxt/content v3 nuxt.config.ts. How could I setup nuxt/content v3 multi language or I should handle by myself in queryCollection?
My website has multi-language but blog system under this site only has en-US, I want to fallback other language to en-US in blog pages when user switch any other language.

[yudin-s]

Nuxt Content v3 does not really have a defaultLocale switch like an i18n module. I would treat localization as part of your content structure and query logic.

If only the blog is available in en-US, keep that collection independent from the current app locale:

const post = await queryCollection("blog")
  .path(`/blog/${slug}`)
  .first()

and do not include the active UI locale in that query.

If you do have localized content later, a common pattern is to store the locale in the path or metadata:

content/blog/en-US/my-post.md
content/blog/fr-FR/my-post.md

Then query the active locale first and fallback to en-US yourself:

const locale = route.params.locale ?? "en-US"

const post =
  await queryCollection("blog").path(`/blog/${locale}/${slug}`).first()
  ?? await queryCollection("blog").path(`/blog/en-US/${slug}`).first()

So short version: yes, handle the fallback in your route/query layer. Nuxt Content provides the collection/query primitives, but it does not decide locale fallback policy for you.