How to solve “No supported encrypter found. The cipher and / or key length are invalid”

Here’s a quick tutorial about solving this common issue:

1. On your project root, open your .env file
2. Look for the APP_KEY setting: it must be a string with 16, 24 or 32 random characters. Just write a string of your choice or, even better, get the md5 hash of something: md5 hashes are 32 characters long.
3. Save and have fun with Laravel!