A fast, smart, & global content delivery network (CDN) for modern(es2015+) web development.
import React from "https://esm.sh/[email protected]"
You may also use a semver or a dist-tag instead of a fixed version number, or omit the version/tag entirely to use the latest
tag:
import React from "https://esm.sh/react" // 18.2.0 (latest)
import React from "https://esm.sh/react@17" // 17.0.2
import React from "https://esm.sh/react@next" // 18.3.0-next-3de926449-20220927
import { renderToString } from "https://esm.sh/[email protected]/server"
or import non-module(js) as following:
import "https://esm.sh/[email protected]/package.json" assert { type: "json" }
You can also import modules/assets from a github repo: /gh/OWNER/REPO[@TAG]/PATH
. For example:
import tslib from "https://esm.sh/gh/microsoft/tslib"
or load a svg image from a github repo: https://esm.sh/gh/microsoft/fluentui-emoji/assets/Alien/Flat/alien_flat.svg
By default, esm.sh rewrites import specifiers based on the package dependencies. To specify the version of these dependencies, you can add the ?deps=PACKAGE@VERSION
query. To specify multiple dependencies, separate them with a comma, like this: [email protected],[email protected]
.
import React from "https://esm.sh/[email protected]"
import useSWR from "https://esm.sh/[email protected]"
You can add the ?external=foo,bar
query to specify external dependencies.
Since these dependencies are not resolved, you need to use import maps to specify the URL for these dependencies. If you are using Deno, you can use the CLI Script to generate and update the import maps that will resolve the external dependencies automatically.
{
"imports": {
"preact": "https://esm.sh/[email protected]",
"preact-render-to-string": "https://esm.sh/[email protected]?external=preact",
}
}
Alternatively, you can mark all dependencies as external by adding a *
prefix before the package name:
{
"imports": {
"preact": "https://esm.sh/[email protected]",
"preact-render-to-string": "https://esm.sh/*[email protected]",
"swr": "https://esm.sh/*[email protected]",
"react": "https://esm.sh/[email protected]/compat",
}
}
Import maps supports trailing slash that can not work with URL search params friendly. To fix this issue, esm.sh provides a special format for import URL that allows you to use query params with trailing slash: change the query prefix ?
to &
and put it after the package version.
{
"imports": {
"react-dom": "https://esm.sh/[email protected]?pin=v117&dev",
"react-dom/": "https://esm.sh/[email protected]&pin=v117&dev/",
}
}
import useSWR from "https://esm.sh/swr?alias=react:preact/compat"
in combination with ?deps
:
import useSWR from "https://esm.sh/swr?alias=react:preact/compat&[email protected]"
The origin idea was coming from @lucacasonato.
By default, esm.sh exports a module with all its exported members. However, if you want to import only a specific set of members, you can specify them by adding a ?exports=foo,bar
query to the import statement.
import { __await, __rest } from "https://esm.sh/tslib" // 7.3KB
import { __await, __rest } from "https://esm.sh/tslib?exports=__await,__rest" // 489B
By using this feature, you can take advantage of tree shaking with esbuild and achieve a smaller bundle size. Note that this feature is only supported for ESM modules and not CJS modules.
import { Button } from "https://esm.sh/antd?bundle"
In bundle mode, all dependencies are bundled into a single JS file except the peer dependencies.
import React from "https://esm.sh/react?dev"
With the ?dev
option, esm.sh builds a module with process.env.NODE_ENV
set to "development"
or based on the condition development
in the exports
field of package.json
. This is useful for libraries that have different behavior in development and production. For example, React will use a different warning message in development mode.
By default, esm.sh checks the User-Agent
header to determine the build target. You can also specify the target
by adding ?target
, available targets are: es2015 - es2022, esnext, deno, and denonext.
import React from "https://esm.sh/react?target=es2020"
Other supported options of esbuild:
- Conditions
import foo from "https://esm.sh/foo?conditions=custom1,custom2"
- Keep names
import foo from "https://esm.sh/foo?keep-names"
- Ignore annotations
import foo from "https://esm.sh/foo?ignore-annotations"
esm.sh supports ?worker
query to load the module as a web worker:
import workerFactory from "https://esm.sh/monaco-editor/esm/vs/editor/editor.worker?worker"
const worker = workerFactory()
You can pass some custom code snippet to the worker when calling the factory function:
const workerAddon = `
self.onmessage = function (e) {
console.log(e.data)
}
`
const worker = workerFactory(workerAddon)
<link rel="stylesheet" href="https://esm.sh/monaco-editor?css">
This only works when the package imports CSS files in JS directly.
esm.sh supports importing wasm modules in JS directly, to do that, you need to add ?module
query to the import URL:
import wasm from "https://esm.sh/@dqbd/[email protected]/tiktoken_bg.wasm?module"
const { exports } = WebAssembly.instantiate(wasm, imports)
If you get an error like ...not provide an export named...
, that means esm.sh can not resolve CJS exports of the module correctly. You can add ?cjs-exports=foo,bar
query to specify the export names:
import { NinetyRing, NinetyRingWithBg } from "https://esm.sh/[email protected]?cjs-exports=NinetyRing,NinetyRingWithBg"
esm.sh is a Deno-friendly CDN that resolves Node's built-in modules (such as fs, os, etc.), making it compatible with Deno.
import express from "https://esm.sh/express";
const app = express();
app.get("/", (req, res) => {
res.send("Hello World");
});
app.listen(3000)
For users using deno < 1.31
, esm.sh uses deno.land/[email protected]/node as node compatibility layer. You can specify a different version by adding the ?deno-std=$VER
query:
import postcss from "https://esm.sh/postcss?deno-std=0.128.0"
Deno supports type definitions for modules with a types
field in their package.json
file through the X-TypeScript-Types
header. This makes it possible to have type checking and auto-completion when using those modules in Deno. (link).
In case the type definitions provided by the X-TypeScript-Types
header are incorrect, you can disable it by adding the ?no-dts
query to the module import URL:
import unescape from "https://esm.sh/lodash/unescape?no-dts"
This will prevent the X-TypeScript-Types
header from being included in the network request, and you can manually specify the types for the imported module.
esm.sh provides a CLI script for managing imports with import maps in Deno. This CLI script automatically resolves dependencies and uses a pinned build version for stability.
To use the esm.sh CLI script, you first need to run the init
command in your project's root directory:
deno run -A -r https://esm.sh init
Once you've initialized the script, you can use the following commands to manage your imports:
# Adding packages
deno task esm:add react react-dom # add multiple packages
deno task esm:add [email protected] # specify version
deno task esm:add react:preact/compat # using alias
# Updating packages
deno task esm:update react react-dom # update specific packages
deno task esm:update # update all packages
# Removing packages
deno task esm:remove react react-dom
To ensure stable and consistent behavior, you may want to pin the build version of a module you're using from esm.sh. This helps you avoid potential breaking changes in the module caused by updates to the esm.sh server.
The ?pin
query allows you to specify a specific build version of a module, which is an immutable cached version stored on the esm.sh CDN.
import React from "https://esm.sh/react-dom?pin=v117"
// or use version prefix
import React from "https://esm.sh/v117/react-dom"
By using the ?pin
query in the import statement, you can rest assured that the version of the module you're using will not change, even if updates are pushed to the esm.sh server. This helps ensure the stability and reliability of your application.
For UI libraries like React and Vue, esm.sh uses a special build version stable
to ensure single version of the library is used in the whole application.
The Global CDN of esm.sh is provided by Cloudflare, one of the world's largest and fastest cloud network platforms.
To host esm.sh by yourself, check the hosting documentation.