Laravel: Syntax error or access violation: 1071 Specified key was too long

This happens because Laravel changed the default value of the fields. To fix this, just go to the file app/Providers/AppServiceProvider.php and add the following code:

use Illuminate\Support\Facades\Schema;

public function boot()
{
    Schema::defaultStringLength(191);
}

Another way to solve is to add the index name in the second parameter:

$table->string('seu_campo')->unique(null,'chave');