Edge Runtime VM

The @edge-runtime/vm package is the low level bindings for creating Web Standard isolated VM contexts under the same Vercel Edge Functions (opens in a new tab) conditions.

It has been designed to simulate Edge conditions locally in your machine.


npm install @edge-runtime/vm

This package includes built-in TypeScript support.


You can evaluate arbitrary code isolated inside a VM context, getting output back from the output:

import { EdgeVM } from '@edge-runtime/vm'
const edgeVM = new EdgeVM()
const promise = edgeVM.evaluate("fetch('')")
const { url, status } = await promise
console.log(`ping to ${url} returned ${status}`)

The @edge-runtime/vm has @edge-runtime/primitives preloaded.

In case you need, you can extend the VM context:

const edgeVM = new EdgeVM({
  extend: (context) => {
    const rawFetch = context.fetch.bind(context.fetch)
    context.fetch = async (input: RequestInfo | URL, init?: RequestInit) =>
        typeof input === 'string' && !input.startsWith('https://')
          ? `https://${input}`
          : String(input),
    return context
const { url, status } = await edgeVM.evaluate("fetch('')")
console.log(`ping to ${url} returned ${status}`)


new EdgeVM([options])

It creates a new EdgeVM instance.


codeGeneration?: object

Provides code generation options to vm.createContext#options (opens in a new tab).

If you don't provide any option, { strings: false, wasm: true } will be used.

extend?: (context: VMContext) => ExtendedDictionary<T>

Allows to extend the VMContext.

const vm = new EdgeVM({
  extend: (context) =>
    Object.assign(context, {
      process: { env: { NODE_ENV: 'development' } },

Note that it must return a contextified object so ideally it should return the same reference it receives.

requireCache?: Map<string, Dictionary>

Provides an initial map to the require cache, if none is given, it will be initialized to an empty map.


evaluate: (code: string): () => Promise<any>

Allows you to run arbitrary code within the VM.

require: (filepath: string)

Allows you to require a CommonJS module referenced in the provided file path within the VM context. It will return its exports.

requireInContext: (filepath: string)

Same as require but it will copy each of the exports in the context of the VM. Exports can then be used inside of the VM with an evaluated script.

requireInlineInContext: (code: string)

Same as requireInContext but allows you to pass the code instead of a reference to a file.

It will create a temporary file and then load it in the VM Context.