Fix Phoenix SECRET_KEY_BASE missing on seenode | Seenode Docs
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Fix Phoenix SECRET_KEY_BASE missing on seenode

Fix Phoenix SECRET_KEY_BASE missing on seenode

Phoenix won't boot on seenode without SECRET_KEY_BASE. Generate one and set it as an environment variable.

The error

Your Phoenix app crashes on startup with something like:

ERROR!! environment variable SECRET_KEY_BASE is missing.
You can generate one by calling: mix phx.gen.secret

or RuntimeError: no :secret_key_base configured.

Quick fix

Phoenix needs a SECRET_KEY_BASE in production. Generate one locally:

Terminal window
mix phx.gen.secret

Set the output as a SECRET_KEY_BASE environment variable on your service, then redeploy. Your config/runtime.exs should read it from the environment (the default generated file already does):

secret_key_base =
  System.get_env("SECRET_KEY_BASE") ||
    raise "environment variable SECRET_KEY_BASE is missing."

Why this happens

SECRET_KEY_BASE signs and encrypts sessions and tokens. It’s a secret, so it isn’t committed to your repo; you must supply it at runtime. Without it, Phoenix refuses to start in production.

Checklist

  • SECRET_KEY_BASE is set on the service and you redeployed.
  • The value is a real generated secret (from mix phx.gen.secret), not a placeholder.
  • config/runtime.exs reads SECRET_KEY_BASE from the environment.