JWT secret format?

On my production Supabase project, the generated JWT secret looks like it's base64 encoded. But in the local development instance the JWT secret is super-secret-jwt-token-with-at-least-32-characters-long, which isn't valid base64.

For context, I'm verifying JWT signatures, so I need to get the JWT secret in bytes. I assumed I could base64 decode the string, but that doesn't work for local development.

How should I be decoding the string?
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