sizes instances based on "Elastic Compute Units". The performance of otherwise identical virtual machines may vary. On November 28, 2017, AWS announced a bare-metal instance, a departure from exclusively offering virtualized instance types.

As of January 2019, the following instance types were offered:
* General Purpose: A1, T3, T2, M5, M5a, M4, T3a
* Compute Optimized: C5, C5n, C4
* Memory Optimized: R5, R5a, R4, X1e, X1, High Memory, z1d
* Accelerated Computing: P3, P2, G3, F1
* Storage Optimized: H1, I3, D2,