AWS quietly launched S3 Files - a way to mount an S3 bucket and work with it like a regular file system. No custom SDK, no aws s3 cp, just standard file operations on top of S3.
How it works
You mount the bucket via a managed endpoint and get a POSIX-compatible interface. Read, write, list - same as a local disk. Your existing tools and applications don’t need to know it’s S3 underneath.
Pricing
There are a few layers to understand:
| Component | Price |
|---|---|
| S3 storage | Standard S3 rates |
| High-performance storage | $0.30 / GB per month |
| High-performance reads | $0.03 / GB per month |
| Standard S3 reads | Free |
| Writes | $0.06 / GB per month |
For a typical mixed read/write workload, the overhead on top of S3 storage comes out to roughly $5 per TB per month. That does not include the underlying S3 storage cost itself.
When it makes sense
If you have applications that expect a file system interface and you don’t want to refactor them to use the S3 API - this fits well. Also useful for sharing large datasets across instances without managing EFS or EBS volumes.
If you’re doing heavy writes or random access at high throughput, the per-GB write cost can add up. Worth running the numbers against EFS before committing.
How it compares to other options
S3 Files is not the only way to mount a bucket. There are four other tools that do roughly the same thing, each with a different trade-off.
Mountpoint for S3
Mountpoint is AWS’s own open-source FUSE driver. Free - you only pay for S3 API calls. It is explicitly not trying to be fully POSIX-compatible. If an operation can’t be done efficiently against the S3 API (rename, hard links, xattr, chmod), it fails instead of emulating it. That is a deliberate choice.
What it is good at: high-throughput sequential reads. ML training jobs, analytics pipelines, anything that reads large files from start to finish. Multiple readers, one writer per file.
What it does not support: random writes, in-place file edits, atomic renames on general-purpose buckets.
s3fs-fuse
s3fs-fuse is older, open-source, and tries harder to look like a real file system. It emulates more POSIX operations than Mountpoint by caching and working around S3 limitations. That makes it more compatible with general-purpose tools but slower and less reliable under concurrent access. Common use case: giving analysts a familiar disk-like interface without changing their tooling.
Also free - pays only for S3 API calls.
Cyberduck
Cyberduck is a desktop GUI client. It is not really a mount - it is a file browser and transfer tool. You drag files in and out, browse the bucket, edit single files. Good for occasional manual access. Not useful for applications that need a mounted path.
CloudMounter
A commercial macOS app. Mounts S3 (and other cloud storage) as a drive in Finder. Aimed at non-technical users who need to work with files without touching a terminal. Reportedly one of the few tools in this category that actually works reliably - several alternatives look polished but fail in practice.
Which one to use
| Tool | Best for | POSIX | Cost |
|---|---|---|---|
| S3 Files | Managed, production, broad compatibility | Yes | Extra per GB |
| Mountpoint | High-throughput reads, ML/analytics | No (by design) | Free |
| s3fs-fuse | General file access, analyst workflows | Partial | Free |
| Cyberduck | Manual browsing, occasional transfers | No | Free / one-time |
| CloudMounter | Non-technical users on macOS | Partial | Paid |
If you’re running workloads in AWS and need a managed solution with broad app compatibility - S3 Files. If you’re optimizing for read throughput and control costs - Mountpoint. If you’re setting up access for analysts who just need a disk - s3fs-fuse. If someone on the team needs to browse a bucket from their Mac without touching a terminal - CloudMounter.