title: “S3 Bucket Configuration” created: 2026-07-20 updated: 2026-07-20 type: knowledge tags:
- aws
- s3
- storage
- certification
S3 Bucket Configuration
What It Is
The set of settings you define when creating an S3 bucket: naming, region placement, object ownership, and default encryption.
Why It Matters
Misconfiguring a bucket at creation time can lead to naming conflicts, latency issues, or security gaps. Several settings (like the bucket name) cannot be changed after creation.
Key Concepts
Bucket Naming Rules
- 3–63 characters
- Lowercase letters, numbers, and hyphens only
- Must start with a letter or number
- Cannot look like an IP address (e.g., 192.168.1.1)
- Globally unique across all AWS accounts and regions
- Immutable — cannot be renamed after creation
Region Selection
- Determines where objects are physically stored
- Affects latency, cost, and regulatory compliance
- Objects never leave a region unless you explicitly transfer them (replication, copy)
Object Ownership
| Setting | Behavior |
|---|---|
| ACLs disabled (default since Apr 2023) | Bucket owner owns all objects; ACLs have no effect |
| ACLs enabled — Bucket owner preferred | Bucket owner owns objects if bucket-owner-full-control ACL is applied |
| ACLs enabled — Object writer | Uploading account retains ownership |
Default Encryption
- SSE-S3 (AES-256) — enabled by default since Jan 2023
- SSE-KMS — use a KMS key for more control
- DSSE-KMS — dual-layer encryption
Gotchas
- Choosing a region cannot be changed after bucket creation
- If ACLs are disabled (recommended), you cannot use “Make public via ACL” — use bucket policies instead
- Bucket names that resemble domain names have extra DNS constraints
See Also
- [[s3-fundamentals]]
- [[s3-block-public-access]]
- [[aws-arns]]