Unsupported cipher or incorrect key length Laravel Origin: Application & API OSI layer 6 · Presentation Last updated 4 Nov 2026

Laravel: RuntimeException: Unsupported cipher or incorrect key length. Supported ciphers are: aes-128-cbc, aes-256-cbc, aes-128-gcm, aes-256-gcm

APP_KEY is missing, malformed or empty, or config/app.php cipher doesn't match the key length.

Exact message you may see Unsupported cipher or incorrect key length. Supported ciphers are: aes-128-cbc, aes-256-cbcRuntimeException: Unsupported cipher or incorrect key lengthUnsupported cipher or incorrect key length LaravelNo application encryption key has been specified. Unsupported cipher
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Seen on: Laravel PHP

Meaning

Generate a key with php artisan key:generate (writes base64:... to .env). Check that .env exists on the server, the key line has no spaces/quotes issues, and config isn't cached with an old/empty key. AES-256 needs 32 bytes; a 16-char key with AES-256-CBC fails.

Common causes

  • APP_KEY empty (no .env on server)
  • Key not base64-prefixed or wrong length
  • Config cached before the key existed
  • .env has APP_KEY= with spaces
  • Cipher changed in config/app.php

⚡ Quick fix

  1. php artisan key:generate
  2. php artisan config:clear
  3. Confirm .env is present and readable by the web user

Detailed fix by platform

Laravel

  1. php artisan key:generate --force && php artisan config:cache

How to diagnose

  1. .env — Present?
  2. Key — base64 32 bytes?
  3. Cache — Rebuilt?

🔧 Still not fixed?

Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:

Where this error sits

Origin: Application & API. Errors that are often confused with or caused by this one (click to open):

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