Segment has a special deduplication service that sits behind the`api.segment.com` endpoint and attempts to drop 99% of duplicate data. Segment stores at least 24 hours worth of event `messageId`s,allowingSegment to deduplicate any data that appearswithin a 24 hour rolling window.

Segment has a special deduplication service that sits behind the`api.segment.com` endpoint and attempts to drop 99% of duplicate data.To achieve it,Segment stores at least 24 hours worth of event `messageId`s,which allowsSegmentsystemsto deduplicate any data that appearswith the same`messageId` within the stored values.

Segment deduplicates on the event's `messageId`,_not_ on the contents of the event payload. Segment doesn't have a built-in way to deduplicate data for events that don't generate`messageId`s.