What are the key differences between Bun and Deno

Performance

- Speed: Bun is designed for high performance, often outperforming both Node.js and Deno in various benchmarks. For instance, Bun can handle approximately 110,000 requests per second with 10 concurrent connections, significantly surpassing Deno's 67,000 and Node.js's 60,000 requests per second[1][4]. This speed advantage is attributed to Bun's use of the JavaScriptCore engine from WebKit and its implementation in Zig, which allows for efficient memory management.

- Startup Time: Bun has a notably faster startup time compared to both Node.js and Deno, making it more suitable for applications where quick initialization is critical[1][2].

Language Support

- TypeScript and JSX: Both Bun and Deno support TypeScript natively without requiring a separate compilation step. This contrasts with Node.js, which typically requires additional tools for TypeScript support[3][5]. However, Bun also includes built-in features like a bundler and test runner, making it a comprehensive toolkit for JavaScript development.

Security

- Security Model: Deno emphasizes security by default, requiring explicit permissions for file system access and network requests. This model is designed to prevent unauthorized access to system resources[1][3]. Bun, while also aiming for security improvements over Node.js, does not enforce the same strict permission model as Deno.

Ecosystem and Compatibility

- Ecosystem Size: Node.js has a vast ecosystem with a rich collection of libraries and tools available through npm. While Deno has made strides in providing compatibility with npm modules (over 2 million), its community is smaller compared to Node.js[3][4]. Bun aims to be a drop-in replacement for Node.js and promises better compatibility with existing npm packages than Deno does[6][7].

- Community Support: As a newer entrant, Bun is still building its community and ecosystem. Deno has an active user base but remains smaller than that of Node.js. The maturity of Node.js provides it with extensive documentation and community resources that are currently unmatched by either Bun or Deno[1][3].

Additional Features

- Bundling and Tooling: Bun includes built-in capabilities for bundling JavaScript applications, which streamlines the development process. In contrast, while Deno offers some built-in tools (like a dependency inspector), it lacks the comprehensive bundling features found in Bun[4][5].

- Development Experience: Developers have noted that while Deno provides a more stable environment for building applications right now, Bun's promise of speed and efficiency makes it appealing for new projects despite some early bugs and stability concerns[6][8].

In summary, while both Bun and Deno offer modern alternatives to Node.js with improved performance and features, they cater to different developer needs. Bun focuses on speed and being a comprehensive toolkit, whereas Deno prioritizes security and simplicity in its design philosophy.