# `Localize.InvalidSubtagError`
[🔗](https://github.com/elixir-localize/localize/blob/v0.39.0/lib/localize/exception/invalid_subtag_error.ex#L1)

Exception raised when an extension key or value is not valid
for a BCP 47 language tag.

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*Consult [api-reference.md](api-reference.md) for complete listing*
