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What is the Deno Standard Library?

The Deno Standard Library is a collection of high-quality, officially supported common utilities for Deno programs. Published on JSR, the standard library provides essential functionality that you can trust and depend on for building robust applications.
The standard library is available at jsr.io/@std and can be imported directly into your Deno projects.

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Key Features

Audited & Maintained

All modules are carefully reviewed and maintained by the Deno core team to ensure quality and security.

Modern JavaScript

Built with modern JavaScript and TypeScript, leveraging web standards and best practices.

Zero Dependencies

Standard library modules have minimal external dependencies, reducing supply chain risks.

Well Documented

Comprehensive documentation and examples for every module and function.

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Available Modules

The Deno Standard Library includes modules for common programming tasks:

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Data Structures & Algorithms

  • collections: Utilities for working with arrays, objects, and other data structures
  • encoding: Encoding and decoding for various formats (base64, hex, csv, json, yaml, etc.)
  • data-structures: Common data structures like binary heaps and red-black trees

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System & I/O

  • fs: File system utilities for reading, writing, and manipulating files
  • path: Cross-platform path manipulation utilities
  • io: Low-level I/O primitives and utilities
  • streams: Utilities for working with web streams

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Text & Formatting

  • fmt: Formatting utilities including colors and printf-style formatting
  • regexp: Regular expression utilities and helpers
  • front-matter: Parse front matter from markdown files

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Network & Web

  • http: HTTP server utilities and helpers
  • ws: WebSocket implementation
  • url: URL parsing and manipulation utilities

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Testing & Quality

  • testing: Testing utilities and assertion functions
  • expect: BDD-style assertion library
  • mock: Mocking utilities for testing

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Utilities

  • async: Async utilities like debounce, delay, and pooling
  • datetime: Date and time manipulation utilities
  • uuid: UUID generation and validation
  • semver: Semantic versioning utilities
  • crypto: Cryptographic utilities
Visit jsr.io/@std for the complete list of available modules and their documentation.

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Design Principles

The Deno Standard Library follows these core principles:
  1. Stability: APIs are carefully designed and changes follow semantic versioning
  2. Quality: All code is thoroughly tested and reviewed
  3. Simplicity: Simple, focused modules that do one thing well
  4. Web Standards: Prefer web platform APIs when available
  5. Type Safety: Full TypeScript support with comprehensive type definitions

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Version Stability

Each module in the standard library is independently versioned, allowing you to:
  • Use different versions of different modules in the same project
  • Upgrade modules incrementally without breaking your application
  • Pin to specific versions for maximum stability
Standard library modules follow semantic versioning. Major version updates may include breaking changes, while minor and patch versions maintain backward compatibility.

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Getting Started

To start using the Deno Standard Library in your project: 
// Import from JSR using the @std namespace
import { assertEquals } from "@std/assert";
import { join } from "@std/path";
import { parse } from "@std/flags";

// Use the imported functions
const filePath = join("src", "main.ts");
console.log(filePath); // "src/main.ts"

Next Steps

Learn how to use standard library modules in your Deno projects

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