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    3.7.1 • Public • Published



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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 S3's 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.

    If your client only supports signed requests, specify the credentials

      accessKeyId: "S3RVER",
      secretAccessKey: "S3RVER",

    in your client's configuration.

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

    Static Website Hosting

    If you specify a website configuration file, S3rver supports simulating S3's static website mode for incoming GET requests.

    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 active 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

    Class: S3rver

    new S3rver([options])

    Creates a S3rver instance

    Option Type Default Description
    address string localhost Host/IP to bind to
    port number 4568 Port of the HTTP server
    key string | Buffer Private key for running with TLS
    cert string | Buffer Certificate for running with TLS
    silent boolean false Suppress log messages
    serviceEndpoint string amazonaws.com Override the AWS service root for subdomain-style access
    directory string Data directory
    resetOnClose boolean false Remove all bucket data on server close
    allowMismatchedSignatures boolean false Prevent SignatureDoesNotMatch errors for all well-formed signatures
    vhostBuckets boolean true Allow vhost-style access for all buckets
    configureBuckets[].name string The name of a prefabricated bucket to create when the server starts
    configureBuckets[].configs[] string | Buffer Raw XML string or Buffer of Bucket config

    For your convenience, we've provided sample bucket configurations you can access using require.resolve:

    const corsConfig = require.resolve('s3rver/example/cors.xml');
    const websiteConfig = require.resolve('s3rver/example/website.xml');
    const s3rver = new S3rver({
      configureBuckets: [
          name: 'test-bucket',
          configs: [fs.readFileSync(corsConfig), fs.readFileSync(websiteConfig)],

    Additional references for defining these configurations can be found here:



    Starts/stops the server on the configured port and host. Returns a Promise if no callback is specified.

    Example in mocha:

    const S3rver = require('s3rver');
    let instance;
    before(function(done) {
      instance = new S3rver({
        port: 4569,
        address: 'localhost',
        silent: false,
        directory: '/tmp/s3rver_test_directory',
    after(function(done) {

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

    Alias: s3rver.getMiddleware()

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

    s3rver.configureBuckets() => Promise<void>

    Convenience method for configurating a set of buckets without going through S3's API. Useful for quickly provisioning buckets before starting up the server.

    s3rver.reset() => void

    Resets all bucket and configurations supported by the configured store.

    Subscribing to S3 Events

    Event: 'event'

    You can subscribe to notifications for PUT, POST, COPY and DELETE object events in the bucket when you run S3rver programmatically. Please refer to AWS's documentation for details of event object.

    const S3rver = require('s3rver');
    const { fromEvent } = require('rxjs');
    const { filter } = require('rxjs/operators');
    const instance = new S3rver({
      port: 4569,
      address: '',
      silent: false,
      directory: '/tmp/s3rver_test_directory',
    }).run((err, { address, port } = {}) => {
      if (err) {
      } else {
        console.log('now listening at address %s and port %d', address, port);
    const s3Events = fromEvent(instance, 'event');
    s3Events.subscribe(event => console.log(event));
      .pipe(filter(event => event.Records[0].eventName == 'ObjectCreated:Copy'))
      .subscribe(event => console.log(event));

    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


    npm i s3rver

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