Standard Library (@std)

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.

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.

Packages Jump to heading#

• @std/assert – Common assertion functions, especially useful for testing
• @std/async – Utilities for asynchronous operations, like delays, debouncing, or pooling
• @std/bytes – Utilities to manipulate Uint8Arrays that are not built-in to JavaScript
• @std/cache – UNSTABLE: Cache utilities
• @std/cbor – UNSTABLE: Utilities for parsing and serializing Concise Binary Object Representation (CBOR)
• @std/cli – Tools for creating interactive command line tools
• @std/collections – Pure functions for common tasks related to collection types like arrays and objects
• @std/crypto – Extensions to the Web Crypto API
• @std/csv – Reading and writing of comma-separated values (CSV) files
• @std/data-structures – Common data structures like red-black trees and binary heaps
• @std/datetime – UNSTABLE: Utilities for dealing with Date objects
• @std/dotenv – UNSTABLE: Parsing and loading environment variables from a .env file
• @std/encoding – Utilities for encoding and decoding common formats like hex, base64, and varint
• @std/expect – Jest compatible expect assertion functions
• @std/fmt – Utilities for formatting values, such as adding colors to text, formatting durations, printf utils, formatting byte numbers.
• @std/front-matter – Extract front matter from strings
• @std/fs – Helpers for working with the file system
• @std/html – Functions for HTML, such as escaping or unescaping HTML entities
• @std/http – Utilities for building HTTP servers
• @std/ini – UNSTABLE: Parsing and serializing of INI files
• @std/internal – INTERNAL: The internal package for @std. Do not use this directly.
• @std/io – UNSTABLE: The utilities for advanced I/O operations using Reader and Writer interfaces.
• @std/json – (Streaming) parsing and serializing of JSON files
• @std/jsonc – Parsing and serializing of JSONC files
• @std/log – UNSTABLE: A customizable logger framework
• @std/media-types – Utility functions for media types (MIME types)
• @std/msgpack – Encoding and decoding for the msgpack format
• @std/net – Utilities for working with the network
• @std/path – Utilities for working with file system paths
• @std/random – UNSTABLE: Various utilities using random number generators. The package also provides seeded pseudo-random number generator.
• @std/regexp – Utilities for working with RegExp
• @std/semver – Parsing and comparing of semantic versions (SemVer)
• @std/streams – Utilities for working with the Web Streams API
• @std/tar – UNSTABLE: Streaming utilities for working with tar archives.
• @std/testing – Tools for testing Deno code like snapshot testing, bdd testing, and time mocking
• @std/text – Utilities for working with text
• @std/toml – Parsing and serializing of TOML files
• @std/ulid – Generation of Universally Unique Lexicographically Sortable Identifiers (ULIDs)
• @std/uuid – Generators and validators for UUIDs
• @std/webgpu – UNSTABLE: Utilities for working with the Web GPU API
• @std/yaml – Parsing and serializing of YAML files

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"));