How to fix "Illuminate\Database\QueryException: SQLSTATE[HY000] [1044] Access denied for user"

Open the .env file and edit it. Just set up correct DB credentials:

DB_CONNECTION=mysql 
DB_HOST=127.0.0.1 
DB_PORT=3306 
DB_DATABASE=            // Your Database Name
DB_USERNAME=           // Yout Database Username
DB_PASSWORD=          // Your Database Password 

The DB_USERNAME should be set to root if you do not have a default username in the installation of MySQL in xampp.

If no password is set on the database, clear it DB_PASSWORD, empty space must also be removed(In the past I've also faceout this problem, window consider blank space as a password)

After completion of .env edit please enter this command in your terminal for clear cache:

php artisan config:cache