Amazon S3 (Simple Storage Service) is an object storage service from Amazon Web Services. Object storage keeps each file as an object (the data plus metadata, found by a key) inside a container called a bucket, instead of in a folder tree on one disk. Programs store and read objects over the internet; the uses AWS names include data lakes for analytics, cloud-native applications and mobile apps.
S3 grows and shrinks automatically, so no storage has to be reserved in advance. AWS states that it is designed for 99.999999999% (11 nines) data durability and 99.99% availability, and data is encrypted by default. Storage classes trade price against access speed, from S3 Standard for frequently used data to S3 Glacier Deep Archive; S3 Intelligent-Tiering moves objects between tiers by access pattern. Newer features include S3 Tables for Apache Iceberg tables and S3 Vectors for vector search.
S3 is billed by usage: per gigabyte stored each month, by storage class and region, plus charges for requests and data transfer.