HTTP 0 – No Response
(AWS ELB) Recorded in load balancer access logs when no status code could be determined, e.g. the client closed the connection before a response, or a health check failed.
Common use case
A log-only marker AWS uses to represent requests that never produced a real HTTP status at all, most often because the client disconnected before anything could be returned.
History
An AWS-specific logging convention, not a real HTTP status code and never sent over the wire.
Did you know?
It is the only entry in this reference that isn't a real HTTP status code at all - it exists purely as a placeholder inside AWS log files for "no status to report".