# Buckets in your code

A bucket speaks S3, so the SDK you'd use for Amazon S3 works with it, given the five variables [connecting an app](/docs/buckets#connecting-an-app) puts in its environment. Two settings differ from Amazon's defaults: **path-style** addressing, and the region `auto`.

## In your code

Buckets use **path-style** addressing and the region `auto`. With the AWS SDK for JavaScript:

```js
import { S3Client, PutObjectCommand } from "@aws-sdk/client-s3";

const s3 = new S3Client({
  endpoint: process.env.S3_ENDPOINT,
  region: process.env.S3_REGION,
  forcePathStyle: true,
  credentials: {
    accessKeyId: process.env.S3_ACCESS_KEY_ID,
    secretAccessKey: process.env.S3_SECRET_ACCESS_KEY,
  },
});

await s3.send(new PutObjectCommand({ Bucket: process.env.S3_BUCKET, Key: "avatars/ada.png", Body: file }));
```

With boto3 (Python):

```python
import os, boto3
from botocore.config import Config

s3 = boto3.client(
    "s3",
    endpoint_url=os.environ["S3_ENDPOINT"],
    region_name=os.environ["S3_REGION"],
    aws_access_key_id=os.environ["S3_ACCESS_KEY_ID"],
    aws_secret_access_key=os.environ["S3_SECRET_ACCESS_KEY"],
    config=Config(s3={"addressing_style": "path"}),
)
```

From your own computer, the AWS CLI works with the key you were shown:

```bash
aws s3 ls s3://uploads-k3m9x2ab --endpoint-url https://storage.smartalfred.com --region auto
```

## Files for browsers

Buckets aren't public: every request is signed with the bucket's key. To let a browser download a file, or upload one straight to the bucket, give it a **presigned URL**, made by your app with its SDK (`getSignedUrl` in JavaScript, `generate_presigned_url` in boto3). Presigned URLs work from any website: there's no CORS to set up.

## What works

Objects in and out, with metadata, ranges and conditional requests; copying within the bucket; listing (with prefixes and delimiters, so folders work); deleting many at once; multipart uploads for large files; presigned URLs.

Not supported: public buckets, versioning, object tags and ACLs, lifecycle rules, and copying between buckets (a key opens one bucket).