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S3rver is a lightweight server that responds to some of the same calls Amazon S3 responds to. It is extremely useful for testing S3 in a sandbox environment without actually making calls to Amazon.

The goal of S3rver is to minimise runtime dependencies and be more of a development tool to test S3 calls in your code rather than a production server looking to duplicate S3 functionality.

Supported methods


  • Create bucket
  • Delete bucket
  • List buckets
  • List content of buckets (prefix, delimiter, marker and max keys, common prefixes)


  • Put object (support for metadata, including ContentEncoding (gzipped files)
  • Post object (multipart)
  • Delete object(s)
  • Get object (including using the HEAD method)
  • Get dummy ACLs for an object
  • Copy object (including updating of metadata)
  • Listen to Put, Copy, Post and Delete events.

Quick Start

Install s3rver:

$ npm install s3rver -g

You will now have a command on your path called s3rver

Executing this command for the various options:

$ s3rver --help

Supported clients

Please see Fake S3s wiki page for a list of supported clients. When listening on HTTPS with a self-signed certificate, the AWS SDK in a Node.js environment will need httpOptions: { agent: new https.Agent({ rejectUnauthorized: false }) } in order to allow interaction.

Please test, if you encounter any problems please do not hesitate to open an issue :)

Static Website Hosting

If you specify an indexDocument then GET requests will serve the indexDocument if it is found, simulating the static website mode of AWS S3. An errorDocument can also be set, to serve a custom 404 page.

Hostname Resolution

By default a bucket name needs to be given. So for a bucket called mysite.local, with an indexDocument of index.html. Visiting http://localhost:4568/mysite.local/ in your browser will display the index.html file uploaded to the bucket.

However you can also setup a local hostname in your /etc/hosts file pointing at


Now you can access the served content at http://mysite.local:4568/


The tests should be run by one of the active LTS versions. The CI Server runs the tests on the latest 6.x and 8.x releases.

To run the test suite, first install the dependencies, then run npm test:

$ npm install
$ npm test

Programmatically running s3rver

You can also run s3rver programmatically.

This is particularly useful if you want to integrate s3rver into another projects tests that depends on access to an s3 environment

new S3rver([options])

Creates a S3rver instance

Option Type Default Description
port number 4578 Port of the mock S3 server
hostname string localhost Host/IP to bind to
key string | Buffer Private key for running with TLS
cert string | Buffer Certificate for running with TLS
silent boolean false Suppress log messages
directory string Data directory
cors string | Buffer S3 Sample policy Raw XML string or Buffer of CORS policy
indexDocument string Index document for static web hosting
errorDocument string Error document for static web hosting
removeBucketsOnClose boolean false Remove all bucket data on server close

Starts the server on the configured port and host

Example in mocha:

const S3rver = require('s3rver');
let instance;
before(function (done) {
    instance = new S3rver({
        port: 4569,
        hostname: 'localhost',
        silent: false,
        directory: '/tmp/s3rver_test_directory'
    }).run((err, host, port) => {
        if(err) {
            return done(err);
after(function (done) {

Subscribing to S3 Event

You can subscribe to Put, Copy,Post and Delete object events in the bucket, when you run s3rver programmatically. Please have a look at Aws page for details of event object. Apply filter function to subscribe to specific events.

const S3rver = require('s3rver');
const client = new S3rver({
        port: 4569,
        hostname: 'localhost',
        silent: false,
        directory: '/tmp/s3rver_test_directory'
    }).run(function (err, host, port) {
        if (err) {
        } else {
            console.log('now listening on host %s and port %d', host, port);

client.s3Event.subscribe(function (event) {

client.s3Event.filter(function (event) { return event.Records[0].eventName == 'ObjectCreated:Copy' }).subscribe(function (event) {

s3rver.callback() ⇒ function (req, res)

Also aliased as s3rver.getMiddleware()

Creates and returns a callback that can be passed into http.createServer() or mounted in an Express app.

Using s3fs-fuse with S3rver

You can connect to s3rver and mount a bucket to your local file system by using the following command:

$ s3fs bucket1 /tmp/3 -o url="http://localhost:4568" -o use_path_request_style -d -f -o f2 -o curldbg