unyaml

Universal YAML loader. Works in Node.js (CJS require / ESM import), esbuild and Vite — one package, one mental model.

Node.js

Node.js ^22.15 || >=24 is required.

From CLI

CJS:

node -r unyaml path/to/index.cjs

ESM:

node --import unyaml path/to/index.mjs

Manually import

CJS:

require('unyaml')
require('path/to/file.yml') // now it works!

ESM:

import 'unyaml'
const data = await import('path/to/file.yml')

esbuild

import esbuild from 'esbuild'
import unyaml from 'unyaml/esbuild'

await esbuild.build({
  entryPoints: ['src/index.ts'],
  bundle: true,
  outfile: 'dist/index.js',
  plugins: [unyaml()],
})

.yml / .yaml imports are loaded, parsed and inlined as JSON modules.

Options

unyaml({
  filter?: RegExp                  // default: /\.ya?ml$/
  // ...plus any js-yaml LoadOptions (schema, json, onWarning, ...)
})

Vite

// vite.config.ts
import { defineConfig } from 'vite'
import unyaml from 'unyaml/vite'

export default defineConfig({
  plugins: [unyaml()],
})

The Vite plugin handles both the main pipeline and the esbuild-based dependency pre-bundling (optimizeDeps), so importing YAML from inside node_modules works out of the box.

Options

unyaml({
  filter?: RegExp                  // default: /\.ya?ml(?:\?.*)?$/
  // ...plus any js-yaml LoadOptions (schema, json, onWarning, ...)
})

TypeScript support

To silence Cannot find module 'file.yml' or its corresponding type declarations. errors, add unyaml/types to compilerOptions.types in tsconfig.json:

{
  "compilerOptions": {
    "types": [
      "unyaml/types"
    ]
  }
}