Serverless S3 Local

A serverless plugin to run a S3 clone on your local machine




serverless npm version MIT licensed npm downloads dependencies dev-dependencies

serverless-s3-local is a Serverless plugin to run S3 clone in local. This is aimed to accelerate development of AWS Lambda functions by local testing. I think it is good to collaborate with serverless-offline.


Use npm

npm install serverless-s3-local --save-dev

Use serverless plugin install

sls plugin install --name serverless-s3-local



service: serverless-s3-local-example
  name: aws
  runtime: nodejs12.x
  - serverless-s3-local
  - serverless-offline
# Uncomment only if you want to collaborate with serverless-plugin-additional-stacks
# additionalStacks:
#    permanent:
#      Resources:
#        S3BucketData:
#            Type: AWS::S3::Bucket
#            Properties:
#                BucketName: ${self:service}-data
    host: localhost
    directory: /tmp
      Type: AWS::S3::Bucket
        BucketName: local-bucket
    handler: handler.webhook
      - http:
        method: GET
        path: /
    handler: handler.s3hook
      - s3: local-bucket
        event: s3:*


const AWS = require('aws-sdk');

module.exports.webhook = (event, context, callback) => {
  const S3 = new AWS.S3({
    s3ForcePathStyle: true,
    accessKeyId: 'S3RVER', // This specific key is required when working offline
    secretAccessKey: 'S3RVER',
    endpoint: new AWS.Endpoint('http://localhost:8000'),
    Bucket: 'local-bucket',
    Key: '1234',
    Body: new Buffer('abcd')
  }, () => {} );

module.exports.s3hook = (event, context) => {

Configuration options

Configuration options can be defined in multiple ways. They will be parsed with the following priority:

  • custom.s3 in serverless.yml
  • custom.serverless-offline in serverless.yml
  • Default values (see table below)
Option Description Type Default value
address The host/IP to bind the S3 server to string 'localhost'
host The host where internal S3 calls are made. Should be the same as address string
port The port that S3 server will listen to number 4569
directory The location where the S3 files will be created. The directory must exist, it won't be created string './buckets'
accessKeyId The Access Key Id to authenticate requests string 'S3RVER'
secretAccessKey The Secret Access Key to authenticate requests string 'S3RVER'
cors The S3 CORS configuration XML. See AWS docs string | Buffer
website The S3 Website configuration XML. See AWS docs string | Buffer
noStart Set to true if you already have an S3rver instance running boolean false
allowMismatchedSignatures Prevent SignatureDoesNotMatch errors for all well-formed signatures boolean false
silent Suppress S3rver log messages boolean false


  • Start local S3 server with specified root directory and port.
  • Create buckets at launching.
  • Support serverless-plugin-additional-stacks
  • Support serverless-webpack
  • Support serverless-plugin-existing-s3
  • Support S3 events.

Working with IaC tools

If your want to work with IaC tools such as terraform, you have to manage creating bucket process. In this case, please follow the below steps.

  1. Comment out configurations about S3 Bucket from resources section in serverless.yml.
#  Resources:
#    NewResource:
#      Type: AWS::S3::Bucket
#      Properties:
#        BucketName: local-bucket
  1. Create bucket directory in s3rver working directory.
$ mkdir /tmp/local-bucket

Triggering AWS Events offline

This plugin will create a temporary directory to store mock S3 info. You must use the AWS cli to trigger events locally. First, using aws configure set up a new profile, i.e. aws configure --profile s3local. The default creds are

aws_access_key_id = S3RVER
aws_secret_access_key = S3RVER

You can now use this profile to trigger events. e.g. to trigger a put-object on a file at ~/tmp/userdata.csv in a local bucket run: aws --endpoint http://localhost:4569 s3 cp ~/tmp/data.csv s3://local-bucket/userdata.csv --profile s3local

You should see the event trigger in the serverless offline console: info: PUT /local-bucket/user-data.csv 200 16ms 0b and a new object with metadata will appear in your local bucket.

See also


This software is released under the MIT License, see LICENSE.

view on Github

Latest commit b2f54ec on Sep 24, 2017

New to serverless?

To get started, pop open your terminal & run:

npm install serverless -g