S3Guard can protect any read/write or read-only S3 bucket. To begin "guarding" a bucket, the first step is to create that bucket if it does not already exist.

Existing buckets can use S3Guard: after creation the data can be imported, though this is not necessary.

Except in when S3Guard is configured to operate in “authoritative mode” (which we do not recommend), clients using S3Guard can work with the same S3 bucket as applications not using S3Guard. Those clients not using S3Guard do not get the consistency, but their use can continue unchanged.