Why Doesn’t Amazon S3 Transfer Acceleration Accept Bucket Names with Periods (.)?

Amazon S3 Transfer Acceleration does not support bucket names that contain a period (.) due to TLS/SSL certificate validation issues.

Here is Why?

S3 Transfer Acceleration Uses CloudFront
- When you enable S3 Transfer Acceleration, AWS routes requests through Amazon CloudFront edge locations to speed up uploads and downloads.
- CloudFront requires valid SSL/TLS certificates for HTTPS communication.
Wildcard SSL Certificates Issue
- AWS uses a wildcard certificate like:
```
  *.s3-accelerate.amazonaws.com
```
- If your bucket name contains a period (.), the hostname will look like:
```
  my.bucket.name.s3-accelerate.amazonaws.com
```
- SSL certificates treat . as a subdomain separator, so my.bucket.name is interpreted as a multi-level subdomain, breaking the wildcard certificate match.
Result: SSL/TLS Name Mismatch Error
- If AWS allowed such bucket names, it would lead to TLS/SSL validation errors and connection failures.

Workarounds:

✅ Use bucket names without periods (.) – Example:

mybucketname.s3-accelerate.amazonaws.com

✅ Use virtual-hosted style URLs with custom domains – Example:

Set up an S3 bucket with a custom domain and use CloudFront with an ACM certificate.
✅ Use path-style URLs for direct S3 access (but note that AWS is deprecating them).

Amazon S3 Naming Convention:

Always follow S3 bucket naming best practices:
🚀 Avoid special characters (., _, etc.).
🚀 Use lowercase letters, numbers, and hyphens (-) only.

Happy Learning 😊