Rails 7.1 Store secret_key_base In Credentials For Local Environment

Rails credentials was introduced in Rails 5.2 and in Rails 7.1, secrets has been deprecated in favor of credentials.

In the latest stable version of Rails (Rails 7.0.6), secrets is used for storing the secret_key_base in the local environment. However, from Rails 7.1 onwards, secret_key_base will be moved to credentials.

What is a secret_key_base?

According to this Rails documentation,

The secret_key_base is used as the input secret to the application’s key generator, which in turn is used to create all ActiveSupport::MessageVerifier and ActiveSupport::MessageEncryptor instances, including the ones that sign and encrypt cookies.

secret_key_base is a randomly generated string which is similar to salt in Cryptography, this value is primarily used to add an extra layer of security to prevent unauthorized users from tampering with cookies, sessions, or other data within the application.

secret_key_base is used by ActiveSupport::MessageVerifier and ActiveSupport::MessageEncryptor.

  • ActiveSupport::MessageVerifier will generate and verify signed messages to prevent tampering.
  • ActiveSupport::MessageEncryptor will encrypt the values in Base64 and we can pass those values safely.

In the local environment, both the development and test secret_key_base value will be fetched from tmp/development_secret.txt(before Rails 7.1) or tmp/local_secret.txt(from Rails 7.1). This file will have the value which will be used as secret_key_base.

For other environments, Rails will first try to get secret_key_base value from ENV["SECRET_KEY_BASE"], then credentials.secret_key_base, and finally secrets.secret_key_base

While building a docker image, we have to precompile assets. In this case, we don’t need to pass the actual secret key instead, we can pass some random values in ENV["SECRET_KEY_BASE_DUMMY"] environment variable which will be stored in secret_key_base.


In the previous version of Rails, the secret_key_base is stored in Rails.application.secrets.secret_key_base.

We can get secret_key_base in the application or from the rails console using the following command,


# "e965987d66462fdf254a9b11aec30dbc27e37e53c01babfd0a52745d66e6f4ad186ee80151628c72cd0c0"


# "e965987d66462fdf254a9b11aec30dbc27e37e53c01babfd0a52745d66e6f4ad186ee80151628c72cd0c0"


With this change, secret_key_base will be stored in Rails.application.credentials.secret_key_base.


# "e965987d66462fdf254a9b11aec30dbc27e37e53c01babfd0a52745d66e6f4ad186ee80151628c72cd0c0"


# DEPRECATION WARNING: `Rails.application.secrets` is deprecated in favor of `Rails.application.credentials` and will be removed in Rails 7.2. (called from eval at /Users/gowsikvivekanandan/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/gems/irb-1.7.4/lib/irb/workspace.rb:113)

# "e965987d66462fdf254a9b11aec30dbc27e37e53c01babfd0a52745d66e6f4ad186ee80151628c72cd0c0"

When attempting to retrieve the secret_key_base value from secrets, a deprecation warning is printed to inform users about the upcoming removal of secrets in Rails 7.2.

Correct way to get secret_key_base:

Instead of accessing secret_key_base from secrets or credentials directly, it is recommended to always retrieve this value by calling Rails.application.secret_key_base.


# "e965987d66462fdf254a9b11aec30dbc27e37e53c01babfd0a52745d66e6f4ad186ee80151628c72cd0c0"

Rails.application.secret_key_base will return the secret_key_base value based on the current environment.

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