Fallback locale for dialects

[riccardolardi]

Does next-intl support something similar to https://github.com/i18next/next-i18next?tab=readme-ov-file#fallback-locales ?

My use case is that the default locale should be de-CH (swiss german) and users with locale de should be forwarded / should fall back to de-CH. Same with it-CH (swiss italian) and fr-CH (swiss french) that should also accept their "native" locale

[amannn]

next-intl doesn't support a "fallback locale", but the most appropriate locale should always be used regardless.

I've just added some tests in e6231f9 to verify this—hope this helps!

[kwunlokng]

The lack of native dialect fallback in next-intl is a real gap — if your de-CH file is missing a key, you'd expect it to resolve from de before falling back to en, but it doesn't.

next-intl-localechain handles exactly this with deep key-level merging:

import { createLocaleChain } from 'next-intl-localechain';

const chain = createLocaleChain({
  'de-CH': ['de-CH', 'de', 'en'],
  'pt-BR': ['pt-BR', 'pt', 'en'],
});

Ships with 75 pre-configured CLDR-based chains so you don't have to map dialect hierarchies yourself.