Rails: Missing encryption key to decrypt file with

Quick fix

Read the commands before running them. Anything that restarts a service, deletes data or changes permissions should be tried on a non-production system first.

# Which credentials file is Rails trying to read?
ls config/credentials.yml.enc config/credentials/*.yml.enc 2>/dev/null

# Get master.key from whoever has it (password manager), then:
cp ~/Downloads/master.key config/master.key
chmod 600 config/master.key

# CI and containers: pass it as an environment variable instead
# RAILS_MASTER_KEY=$(cat config/master.key)

# Per-environment credentials use their own key
# config/credentials/production.key

# Verify it decrypts
bin/rails credentials:show | head -3

# Key truly lost? Start again and re-enter every secret
# rm config/credentials.yml.enc && bin/rails credentials:edit

How to diagnose Ruby errors

Ruby errors are dominated by Bundler and gem resolution, native extension compilation (which needs system headers Ruby cannot install for you), and in Rails by the pending-migration and asset-precompilation guards. Those guards are deliberate safety checks, so the fix is to satisfy them rather than to disable them.

If the quick fix above does not resolve it, work through these steps. They apply to this whole class of error, not just to this one message, which is usually what saves the time.

1. Run bundle install with verbose output and read which gem fails and why. Native extension failures name the missing header in the mkmf log.
2. Check the mkmf log path the error prints. It contains the actual compiler error, which the Bundler summary truncates.
3. For Rails migration errors, run rails db:migrate:status to see exactly which migrations the database has recorded.
4. For asset errors in production, confirm rails assets:precompile ran during deployment and that the manifest is present in public/assets.
5. Verify the Ruby version matches .ruby-version and the Gemfile. Version managers silently switch, producing gem-not-found errors for gems that are installed elsewhere.

Tools worth reaching for

• bundle install --verbose
• rails db:migrate:status
• gem env
• rbenv/rvm version check
• bundle exec

Authoritative references

Primary documentation for this error, worth reading before applying any fix in production.

📖 guides.rubyonrails.org

Related Ruby errors

• Bundler: Could not find gemBundler cannot locate the specified gem in any of the configured sources (e.g., RubyGems).
• Bundler: Your bundle only supports platforms ["arm64-darwin-23"]Gemfile.lock records the platforms it was resolved for, and it was generated on a Mac, so the…
• Encoding::InvalidByteSequenceErrorA string contains bytes that are invalid for the expected encoding (e.g., invalid UTF-8 bytes).
• LoadError: cannot load such fileRuby cannot find the required file or gem. The gem may not be installed, or the require path…
• Rails: ActionController::InvalidAuthenticityTokenThe CSRF token in the request did not match the one in the session. Rails keeps the session…
• Rails: ActiveRecord::NoDatabaseError: We could not find your databaseRails reached the database server and logged in, but the database it asked for does not exist…
• Rails: Asset not precompiledA referenced asset (CSS, JS, image) was not included in the precompiled asset list for…
• Rails: Blocked hosts: myapp.example.comThis is Rails' own HostAuthorization middleware, added in Rails 6 to stop DNS rebinding…

See all 20 Ruby errors →

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Something missing or wrong?

This entry is maintained by hand. If the fix is out of date, incomplete, or you have a better one, email a correction and it will be reviewed.