defaultLocale is not working and always uses en

[rezaaa]

This is my middleware, and my defaultLocale is "fa" but it doesn't work and uses the en as the default when I delete en or change the en to another language like fr, the default locale works!

import { NextRequest } from "next/server"
import { withAuth } from "next-auth/middleware"
import { createI18nMiddleware } from "next-international/middleware"

const locales = ["fa", "en"]
const publicPages = ["/", "/auth"]

const I18nMiddleware = createI18nMiddleware({
  locales,
  defaultLocale: "fa",
})

const authMiddleware = withAuth((req) => I18nMiddleware(req), {
  callbacks: {
    authorized: ({ token }) => token != null,
  },
  pages: {
    signIn: "/auth",
  },
})

export default function middleware(req: NextRequest) {
  const publicPathnameRegex = RegExp(
    `^(/(${locales.join("|")}))?(${publicPages.join("|")})?/?$`,
    "i"
  )
  const isPublicPage = publicPathnameRegex.test(req.nextUrl.pathname)

  if (isPublicPage) {
    return I18nMiddleware(req)
  } else {
    return (authMiddleware as any)(req)
  }
}

export const config = {
  matcher: ["/((?!api|static|.*\\..*|_next|favicon.ico|robots.txt).*)"],
}

[QuiiBz]

That's related to how the locale is resolved by default: we're extracting the Accept-Language header and trying to find a locale (within the locales option) that matches. If one is found, this locale is used, and defaultLocale isn't - the latter is only used when we cannot find any matching locale with the Accept-Language header.

You can override this logic using the resolveLocaleFromRequest option: https://next-international.vercel.app/docs/app-middleware-configuration#override-the-users-locale-resolution

In your case, you'll likely want to return "fa", if you always want your users to use this locale by default, instead of using their preferred one if available.