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Standard Library

Deno provides a standard library written in TypeScript. It is a set of standard modules that can be reused by programs, allowing you to focus on your application logic rather than "reinventing the wheel" for common tasks. All of the modules in the Deno Standard Library are audited by the core team and are guaranteed to work with Deno, ensuring consistency and reliability.

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Many packages in the Deno Standard Library are also compatible with Node.js, Cloudflare Workers, and other JavaScript environments. This allows you to write code that can be run in multiple environments without modification.

The standard library is hosted on JSR and is available at: https://jsr.io/@std. Packages are documented, tested, and include usage examples. You can browse the full list of standard library packages on JSR, but here are a few examples:

  • @std/path: Path manipulation utilities, akin to Node.js's path module.
  • @std/jsonc: (De)serialization of JSON with comments
  • @std/encoding: Utilities for encoding and decoding common formats like hex, base64, and variant

Versioning and stability Jump to heading

Each package of the standard library is independently versioned. Packages follow semantic versioning rules. You can use version pinning or version ranges to prevent major releases from affecting your code.

Importing standard library modules Jump to heading

To install packages from the Deno Standard Library, you can use the deno add subcommand to add the package to your deno.json import map.

deno add jsr:@std/fs jsr:@std/path

The deno.json imports field will be updated to include those imports:

{
  "imports": {
    "@std/fs": "jsr:@std/fs@^1.0.2",
    "@std/path": "jsr:@std/path@^1.0.3"
  }
}

You can then import these packages in your source code:

import { copy } from "@std/fs";
import { join } from "@std/path";

await copy("foo.txt", join("dist", "foo.txt"));

Alternatively, you can import modules directly with the jsr: specifier:

import { copy } from "jsr:@std/fs@^1.0.2";
import { join } from "jsr:@std/path@^1.0.3";

await copy("foo.txt", join("dist", "foo.txt"));

Node.js compatibility Jump to heading

The Deno Standard Library is designed to be compatible with Node.js, Cloudflare Workers, and other JavaScript environments. The standard library is written in TypeScript and compiled to JavaScript, so it can be used in any JavaScript environment.

npx jsr add @std/fs @std/path

Running this command will add those packages to your package.json:

{
  "dependencies": {
    "@std/fs": "npm:@jsr/std__fs@^1.0.2",
    "@std/path": "npm:@jsr/std__path@^1.0.3"
  }
}

Then you can import them in your source code, just like you would with any other Node.js package. TypeScript will automatically find the type definitions for these packages.

import { copy } from "@std/fs";
import { join } from "@std/path";

await copy("foo.txt", join("dist", "foo.txt"));