serverless-webpack

5.15.4 verified Sat Apr 25 auth: no javascript

A Serverless Framework plugin that bundles Lambda function code using Webpack, enabling tree-shaking, individual packaging, Babel transpilation, and custom loaders. Current stable version is 5.15.4, released April 2025. Requires Node.js >= 20 and supports Serverless v1 through v4 (with esbuild disabled in v4). Active development with monthly releases. Compared to serverless-bundle or serverless-esbuild, this plugin offers broader Webpack version support (3, 4, 5), NPM/Yarn packaging, async webpack config, and seamless integration with serverless-offline.

Common errors

error Error: Cannot find module 'serverless-webpack' ↓

cause Plugin not installed or not in devDependencies.

fix

Run npm install serverless-webpack --save-dev.

error Configuration error: Cannot resolve 'webpack' ↓

cause Missing webpack as a devDependency.

fix

Run npm install webpack --save-dev.

error TypeError: slsw.lib.serverless.providers.aws.getAccountId is not a function ↓

cause Using async webpack config outside of Lambda edge context.

fix

Ensure you are using the correct slsw object from the plugin; check serverless version compatibility.

error Error: spawn EINVAL ↓

cause Node > 20.12.2 on Windows, older serverless-webpack version.

fix

Upgrade serverless-webpack to v5.14.0+.

Warnings

breaking Node.js >= 20 required as of v5.15.4. Node 18 dropped in v5.15.4, Node 16 dropped in v5.14.0. ↓

fix Upgrade Node.js to version 20 or later.

breaking Serverless v4 requires disabling built-in esbuild: set build.esbuild: false in serverless.yml. ↓

fix Add build: esbuild: false to serverless.yml.

breaking Removed is-builtin-module dependency in v5.15.4. Might break if relying on that polyfill. ↓

fix Ensure your code does not depend on is-builtin-module being available.

deprecated Serverless v1-v3 support may be dropped in future releases. The peer dependency allows v4. ↓

fix Migrate to Serverless v4 if needed.

gotcha Native ESM output requires copyPackageSectionNames config and may need package.json adjustments. ↓

fix Use copyPackageSectionNames in custom.webpack and ensure package.json has required fields.

gotcha E2E tests and some features may fail on Windows due to spawn EINVAL on Node > 20.12.2 (fixed in v5.14.0). ↓

fix Upgrade to v5.14.0+ or use Node <= 20.12.2 on Windows.

gotcha When using serverless-offline, webpack config must not have mode: 'production' to allow source maps. ↓

fix Use mode: 'development' or set devtool appropriately for local runs.

Install

npm install serverless-webpack

yarn add serverless-webpack

pnpm add serverless-webpack

Imports

default
wrong
```
plugins:
  - serverless-webpack-plugin
```
correct
```
plugins:
  - serverless-webpack
```
Plugins in serverless.yml use the package name directly, no import statement.
slsw
wrong
```
import slsw from 'serverless-webpack'
```
correct
```
const slsw = require('serverless-webpack')
```
The module exports a single function via module.exports, not ESM. Use require() in webpack.config.js.
lib
wrong
```
slsw.default.lib
```
correct
```
slsw.lib
```
slsw.lib provides access to serverless instance and other utilities. No default export.
ServerlessWebpack (TypeScript)
wrong
```
const ServerlessWebpack = require('serverless-webpack').default;
```
correct
```
import ServerlessWebpack from 'serverless-webpack';
```
TypeScript typings allow default import, but the CJS runtime still works. Prefer import syntax for type safety.

Quickstart

Initialize a Serverless service with serverless-webpack, install plugin, configure webpack for Node.js target, and create a basic handler.

npm install serverless-webpack --save-dev

# serverless.yml
service: my-service
plugins:
  - serverless-webpack
provider:
  name: aws
  runtime: nodejs20.x
custom:
  webpack:
    webpackConfig: 'webpack.config.js'
    includeModules: false
functions:
  hello:
    handler: handler.hello

// webpack.config.js
const path = require('path');
module.exports = {
  entry: './handler.js',
  target: 'node',
  output: {
    libraryTarget: 'commonjs2',
    path: path.join(__dirname, '.webpack'),
    filename: '[name].js',
  },
};

// handler.js
exports.hello = async (event) => {
  return { statusCode: 200, body: 'Hello from serverless-webpack!' };
};