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serverless-bundle is a Serverless Framework plugin that optimally packages your ES6 or TypeScript Node.js Lambda functions with sensible defaults so you don't have to maintain your own Webpack configs. It uses the serverless-webpack plugin internally.

  • Only one dependency
  • Supports ES6 and TypeScript
  • Generates optimized packages
  • Linting Lambda functions using ESLint
  • Supports transpiling unit tests with babel-jest
  • Source map support for proper error messages
  • Support esbuild and esbuild-loader for faster builds

And all this works without having to install Webpack, Babel, ESLint, esbuild, etc. or manage any of their configs. Simply add serverless-bundle to your app and you are done!

-    "eslint"
-    "webpack"
-    "ts-loader"
-    "typescript"
-    "css-loader"
-    "graphql-tag"
-    "@babel/core"
-    "babel-eslint"
-    "babel-loader"
-    "eslint-loader"
-    "esbuild-loader"
-    "@babel/runtime"
-    "@babel/preset-env"
-    "serverless-webpack"
-    "source-map-support"
-    "webpack-node-externals"
-    "eslint-config-strongloop"
-    "tsconfig-paths-webpack-plugin"
-    "fork-ts-checker-webpack-plugin"
-    "@babel/plugin-transform-runtime"
-    "babel-plugin-source-map-support"

+    "serverless-bundle"

You can read more about this over on the SST Guide.

💥 The serverless-bundle team recently launched the SST. SST makes it easy to build serverless apps by letting you test your Lambda functions live. It's based on the many of ideas behind serverless-bundle.

Table of Contents

Getting Started

Install the serverless-bundle plugin using:

$ npm install --save-dev serverless-bundle

Then add it to your serverless.yml.

  - serverless-bundle

To run your tests using the same Babel config used in the plugin add the following to your package.json:

"scripts": {
  "test": "serverless-bundle test"

We also have a couple of template repos to help you get started:


Once installed and added to your serverless.yml, serverless-bundle will automatically package your functions using Webpack when you run the various serverless commands.


You can configure the following through your serverless.yml. Note that, these are all optional.

    sourcemaps: true                # Enable source maps
    caching: true                   # Enable Webpack caching
    concurrency: 5                  # Set desired concurrency, defaults to the number of available cores
    stats: false                    # Don't print out any Webpack output
    linting: true                   # Enable linting as a part of the build process
    generateStatsFiles: false       # Creates stats files that could be used for bundle analyzing, more below
    esbuild: false                  # Use esbuild-loader instead of babel or ts for faster builds
    disableForkTsChecker: false     # Disable the ForkTsChecker plugin, more below
    tsConfig: "tsconfig.json"       # Path to your 'tsconfig.json', if it's not in the root
    forceInclude:                   # Optional list of NPM packages that need to be included
      - mysql                         # Only necessary if packages are included dynamically
    ignorePackages:                 # Ignore building any of the following packages
      - hiredis                       # For ex, hiredis needs to be ignored if using redis
    externals:                      # Set non Webpack compatible packages as externals
      - isomorphic-webcrypto          # They'll be included in the node_modules/, more below
    forceExclude:                   # Don't include these in the package
      - chrome-aws-lambda             # Because it'll be provided through a Lambda Layer
    excludeFiles: "**/*.test.ts"    # Exclude files from Webpack that match the glob
    fixPackages:                    # Include fixes for specific packages
      - "formidable@1.x"              # For ex, formidable@1.x doesn't work by default with Webpack
    copyFiles:                      # Copy any additional files to the generated package
      - from: 'public/*'              # Where the files are currently
        to: './'                      # Where in the package should they go
    aliases:                        # Create an alias to 'import' modules easily with a custom path
      - Lib: custom-lib/src/lib       # For ex, replace the long 'custom-lib/src/lib' with 'Lib'
    packager: npm                   # Specify a packager, 'npm' or 'yarn'. Defaults to 'npm'.
    packagerOptions:                # Run a custom script in the package process
      scripts:                        #
        - echo hello > test
    nodeModulesRelativeDir: '../'   # Useful for monorepos if you have your node_modules in the root directory
    rawFileExtensions:              # An array of file extensions to import using the Webpack raw-loader.
      - csv                         # Defaults to ['pem', 'txt']
    minifyOptions:                  # Options for ESBuildMinifyPlugin (
      keepNames: true               # Disable symbol name mangling during minification
    experiments:                    # Give the ability to activate and try out experimental features of Webpack

Advanced Options

  • ESLint

    This plugin uses eslint-config-strongloop. You can override this by placing your own .eslintrc.json with the rules you'd like to use. If you'd like to ignore specific files, you can use a .eslintignore file.

  • Customizing Babel and Webpack configs

    This plugin does not support customizing the Babel and Webpack configs, since serverless-webpack does a pretty good job with that. However, if you think the default config is missing some key features, feel free to open an issue about it.

  • Supporting specific packages

    Certain packages like (formidable@1.x) do not work with Webpack without customizing the config. To support these packages, we use the fixPackages option. This allows us to customize the Webpack config without having folks learn about the internals of Webpack, or maintaining their own complicated configs. If a specific package doesn't work without customizing the Webpack config, add to the fixPackages option and submit a PR.

  • Packager scripts

    The packagerOptions.scripts option allows serverless-webpack to run a custom script in the packaging process. This is useful for installing any platform specific binaries. See below for the sharp package.

  • Aliases

    Import paths can get very long when dealing with complicated directory structures in monorepo apps. The aliases option allows you to define a shorter version. So if you have an import that looks like:

    import Utility from '../../custom-lib/src/lib/utility';

    Adding the following. Where src/utilities is the path from the project root.

          - "Lib": custom-lib/src/lib

    This would allow you to instead import using the following, from anywhere in your project.

    import Utility from 'Lib/utility';

    To use aliases in your tests you'll need to use Jest's moduleNameMapper. Add the following your package.json:

    "jest": {
      "moduleNameMapper": {
        "Lib(.*)$": "<rootDir>/custom-lib/src/lib/$1"
  • Excluding modules from bundling

    In some cases it might be neccessary to exclude certain modules from bundling with Webpack. This can be achieved by setting the module alias to false:

          - "module-name": false

    The aliases option is explained in detail in the Webpack documentation.

  • Usage with WebStorm

    Here is some info on how to get this plugin to support running tests in WebStorm — #5 (comment)

  • Alternative Jest Result Processor

    For CI services (like Atlassian Bamboo CI) that do not work with Jest test results, start by installing jest-mocha-reporter.

    To set the testResultsProcessor option, add "testResultsProcessor": "jest-mocha-reporter" to the Jest section in your package.json. You should see the default command line output when running npm run test, but you should also get a test-report.json.

    To test the reporters option, add "reporters": ["jest-mocha-reporter"] instead. This should result in the same file as above but without the command line output.


If serverless-bundle detects a tsconfig.json in your service root, it'll enable TypeScript.

You can also change where your tsconfig is.

    tsConfig: 'tsconfig.special.json'

Module and Targets

Setting the module to commonjs or target to es3 or es5 conflicts with the babel-plugin-source-map-support plugin that serverless-bundle uses for adding source maps. It'll cause imports in your code to error out with something like this:

TypeError: fileName.functionName is not a function

So if serverless-bundle detects these in your tsconfig.json, it'll print the following warning.

serverless-bundle: CommonJS, ES3, or ES5 are not supported

More on this issue here.


By default serverless-bundle uses the ForkTsCheckerWebpackPlugin to speed up builds by running type checking in a separate process. However, this combined with Serverless Framework's package: individually: true option means that to packages each Lambda function, a separate type checking process is started. Concurrently, starting many such processes can cause your build process to run out of memory.

To disabled this, add the following to your config.

    disableForkTsChecker: true

Package Specific Config

The packages below need some additional config to make them work.


The knex.js module is automatically excluded from the bundle since it's not compatible with Webpack. However, you need to force include the specific database provider package since these are dynamically included. Use the forceInclude option to pass in a list of packages that you want included. For example, to include mysql use the following:

      - mysql


The sharp package needs to include a specific binary before package. Use the packagerOptions.scripts for this.

        - rm -rf node_modules/sharp && npm install --arch=x64 --platform=linux --target=10.15.0 sharp


The pg package optionally includes pg-native that needs to be ignored from Webpack. Use the ignorePackages option to do this.

      - pg-native


The redis package optionally includes hiredis that needs to be ignored from Webpack. Use the ignorePackages option to do this.

      - hiredis


To use the Sequelize package along with pg, you'll need to ignore it from Webpack and using the dialectModule option. Read more here.

In your serverless.yml:

      - pg-native

And in your Lambda code:

const sequelize = new Sequelize(
    host: process.env.DB_HOST,
    dialect: process.env.DB_DIALECT,
    dialectModule: pg

Formidable 1.x

Formidable 1.x doesn't work with Webpack by default. We have a fix that we apply to the Webpack config for it to work. To apply the fix use the following:

      - "formidable@1.x"

If enabled, Webpack adds the following definition to work with Formidable — { "global.GENTLY": false }.

Nested Services

It's common in Serverless monorepo setups that the plugins are installed at the root level and referenced in the individual services. Take the following project setup:

package.json          // Here serverless-bundle is installed
  |- package.json     // Can run npm test from here, referring to parent `package.json`
  |- handler.js
  |- handler.test.js
  |- serverless.yml   // Uses serverless-bundle plugin
  |- package.json     // Can run npm test from here, referring to parent `package.json`
  |- handler.js
  |- handler.test.js
  |- serverless.yml   // Uses serverless-bundle plugin

Running Serverless commands (deploy, package, etc.) from the services directories are supported out of the box. To get your tests to run correctly, you need to do the following.

In the root package.json use the following test script:

"scripts": {
  "test": "serverless-bundle test"

And in service1/package.json use this test script:

"scripts": {
  "test": "npm --prefix ./../ test service1"

This tells serverless-bundle (in the root) to only run the tests inside the service1/ directory. As opposed to the entire project.

CSS and SASS Files

Serverless Bundle automatically supports importing css and scss using the isomorphic-style-loader.

import "./assets/style.css";
import "./assets/style.scss";

Support for pem, txt, and other raw files

Serverless Bundle automatically supports importing .pem and .txt, using the Webpack raw-loader.

import "./assets/key.pem";
import "./assets/text.txt";

If you need load additional files using the raw-loader, you can use the rawFileExtensions config option.

      - csv


The externals option takes a list of packages or all. By default this is set to ["knex", "sharp"].

Packages listed in externals are ignored by Webpack. They are instead added in the node_modules/ directory of the Lambda .zip file. These usually include npm packages that are not supported by Webpack.

The all option allows you to list all the packages in YOUR node_modules/ directory as externals. This might be useful in cases where they are just too many to list. Or you are using something like EJS that implicitly requires a long list of packages that are not supported by Webpack.

Note that, adding a package to the externals list might make your Lambda .zip file larger. This is because the entire package directory is zipped. Instead of using Webpack to just include the code that is necessary. So it's advisable to avoid using the all option.

If you think we should add to the default list of externals, open a PR.

Example of specifying a list of packages:

      - knex
      - sharp

Example of using the all option:

    externals: all

Externals vs forceExclude vs excludeFiles

The three options (externals, forceExclude, and excludeFiles) look similar but have some subtle differences. Let's look at them in detail:

  • externals

    These are packages that need to be included in the Lambda package (the .zip file that's sent to AWS). But they are not compatible with Webpack. So they are marked as externals to tell Webpack not bundle them.

  • forceExclude

    These packages are available in the Lambda runtime. Either by default (in the case of aws-sdk) or through a Lambda layer that you might be using. So these are not included in the Lambda package. And they are also marked as externals. Meaning that packages that are in forceExclude are automatically added to the externals list as well. By default, aws-sdk is listed in the forceExclude when runtime is lower than nodejs18.x.

  • excludeFiles

    These are a glob of files that can be excluded from the function resolution. This happens when you have multiple files that are in the same directory and Serverless Framework tries to use them as a function handler. For example, if you have a index.js and a index.test.js and your function is pointing to index, you'll get a warning saying, WARNING: More than one matching handlers found for index. Using index.js. To fix this, use excludeFiles: **/*.test.js.

Generating stats files

Use the generateStatsFiles option if you want to analyze your bundle size. This option, if set to true, will enable the generation of a bundle_stats.json and a bundle_stats.html in the output directory, using the webpack-bundle-analyzer plugin.


  • Open a new issue if you've found a bug or have some suggestions.
  • Or submit a pull request!

Running Locally

To run this project locally, clone the repo and initialize the project.

$ git clone
$ cd serverless-bundle
$ npm install

Run all the tests.

$ npm test

To test the serverless-bundle test command.

$ npm run test scripts

To install locally in another project.

$ npm install /path/to/serverless-bundle


  1. Label the PRs with breaking, enhancement, bug, documentation, or internal
  2. Merge the PRs
  3. Generate changelog npm run changelog
  4. Draft a new release with the changelog
  5. Up the version based on the PR labels npm version <major|minor|patch>
  6. Push the tag git push origin <tag_name>
  7. Publish to npm npm publish
  8. Update the tag in release and publish release notes


This plugin would not be possible without the amazing serverless-webpack plugin and the ideas and code from Create React App.

This plugin is maintained by SST.