Cross-zone load balancing is enabled by default for Application Load Balancers (and cannot be disabled), disabled by default for Network Load Balancers and Gateway Load Balancers, and disabled by default for Classic Load Balancers (with no data transfer charge if enabled) [citation:3][citation:6].
Cross-zone load balancing behavior differs across load balancer types [citation:3][citation:6]:
Application Load Balancer (ALB): Enabled by default and cannot be disabled at the load balancer level. You can disable it at the target group level. There are no charges for inter-AZ data when enabled.
Network Load Balancer (NLB) & Gateway Load Balancer (GWLB): Disabled by default. If you enable it, you incur charges for inter-AZ data.
Classic Load Balancer (CLB): Disabled by default. You can enable it via the console or API. If you enable it, there are no charges for inter-AZ data.