You're choosing a JavaScript runtime. Should you prioritize security-first design with broad community input, or speed-first execution with tight core team control?
Using Collab.dev, we analyzed the last 100 pull requests from both repositories to understand how each runtime manages development at scale.
🎯 Runtime Overview
Deno is a secure-by-default JavaScript and TypeScript runtime created by Node.js creator Ryan Dahl. Built on V8, Rust, and Tokio, Deno requires explicit permissions for file, network, and environment access. The runtime includes built-in tooling (formatter, linter, test runner, bundler) and a curated standard library, eliminating the need for external build tools.
Bun is a performance-focused JavaScript runtime built on JavaScriptCore (Safari's engine). Positioning itself as a drop-in Node.js replacement, Bun emphasizes speed across all operations: runtime execution, package installation, bundling, and testing. The runtime includes native TypeScript and JSX support, a bundler, transpiler, and package manager—all in a single binary.
Deno focuses on security and developer experience through better defaults; Bun focuses on raw performance and Node.js compatibility.
🔧 Technical Philosophy
Deno uses URL-based imports instead of npm packages, eliminating node_modules directories. TypeScript works without configuration. The permission system requires explicit flags (--allow-net, --allow-read) for any system access, preventing unauthorized operations. Standard library modules are version-locked and audited by the Deno team. Web platform APIs (fetch, WebSocket, Web Crypto) work identically to browsers.
Bun maintains npm compatibility, supporting package.json and node_modules workflows. Package installation claims 25x faster speeds than npm. The JavaScriptCore engine provides faster startup times than V8-based runtimes. Built-in APIs extend beyond web standards for maximum performance. Hot reloading, environment variable loading, and test running require no external dependencies.
Deno: security through constraints and web standards alignment. Bun: speed through optimization and developer convenience.
⚡ Collaboration Metrics Comparison
| Metric | Deno | Bun |
|---|---|---|
| Community Contributions | 28% | 6% |
| Core Team Contributions | 68% | 92% |
| Review Coverage | 100% | 76% |
| Median Review Turnaround | 3h 19m | 6m 53s |
| Median Merge Time | 15h 5m | 15h 3m |
| Review Within 1 Hour | 37.6% | 70.8% |
| Review Within 4 Hours | 52.7% | 89.2% |
Deno's 28% community ownership and 100% review coverage reflect a quality-focused approach where every change undergoes thorough review. The 3h 19m median review turnaround balances community participation with careful vetting—critical for a security-first runtime.
Bun's 92% core team ownership and 6m 53s median review turnaround enable rapid iteration. The 76% review coverage allows faster merges for trusted contributors while maintaining quality for complex changes. This velocity supports Bun's aggressive performance optimization cycle.
🏗 Architecture Decisions
Deno built on Rust provides memory safety guarantees and prevents entire classes of vulnerabilities. The V8 engine maintains compatibility with Chrome and Edge browser behavior. URL imports enable decentralized package hosting—no central registry required. Explicit permissions make Deno suitable for running untrusted code in sandboxed environments.
Bun built on Zig enables low-level optimizations for speed. JavaScriptCore's faster startup and lower memory footprint benefit CLI tools and serverless functions. Node.js API compatibility means existing npm packages work without modification. The single-binary distribution (no separate tools) simplifies deployment and reduces installation time.
💼 Ecosystem Position
Deno positions as the secure runtime for cloud-native applications, edge computing, and environments requiring sandboxed execution. Deno Deploy provides serverless infrastructure optimized for Deno's architecture. The runtime targets teams prioritizing security, TypeScript-first development, and web standards alignment. Growing adoption in regulated industries and multi-tenant platforms.
Bun positions as the high-performance runtime for speed-critical applications, developer tooling, and Node.js migration paths. The runtime targets teams optimizing build times, test execution, and cold start performance. Adoption growing among developers frustrated with Node.js tooling complexity and teams seeking infrastructure cost reduction through faster execution.
🔍 When Each Runtime Fits
Choose Deno When
- Security is non-negotiable (untrusted code execution, sandboxing requirements)
- TypeScript-first development without build configuration
- Building for edge computing or serverless with Deno Deploy
- Web standards alignment matters for browser/runtime code sharing
- Team values opinionated tooling and curated standard library
- Permission-based access control matches security model
Choose Bun When
- Performance is the primary concern (startup time, execution speed, build times)
- Migrating from Node.js with minimal code changes
- Package installation speed impacts developer productivity
- Single-binary deployment simplifies infrastructure
- Team needs all-in-one tooling (runtime, bundler, test runner, package manager)
- Cold start optimization matters for serverless or CLI tools
💡 Development Philosophy
Deno embodies "secure by default" through careful design and community oversight. The 100% review coverage and 28% community contribution rate reflect a runtime where security and correctness outweigh speed of iteration. Every change faces scrutiny because Deno's security guarantees depend on thorough vetting. The higher community participation (compared to Bun) suggests a runtime open to external ideas while maintaining quality standards.
Bun prioritizes "ship fast, optimize everything" through tight core team control and rapid iteration. The 92% core team contribution rate and 6m 53s median review turnaround enable aggressive performance optimization. The 76% review coverage allows quick merges for low-risk changes while maintaining oversight for complex features. This velocity supports Bun's mission to outperform existing runtimes on every benchmark.
Both succeed by aligning collaboration patterns with runtime goals: security through thorough review vs. performance through rapid iteration.
Want to analyze collaboration patterns in your open-source project? See how your PR metrics compare with Collab.dev.
TL;DR
Deno offers security-first JavaScript/TypeScript runtime with 28% community ownership and 100% review coverage, optimized for secure cloud-native applications, edge computing, and TypeScript-first development. URL-based imports, explicit permissions, and built-in tooling eliminate traditional Node.js pain points.
Bun offers performance-first JavaScript runtime with 92% core team ownership and 6m 53s median review turnaround, optimized for speed-critical applications and Node.js migration. JavaScriptCore engine, npm compatibility, and all-in-one tooling deliver faster execution across every operation.
Both challenge Node.js but solve different problems: security through constraints vs. performance through optimization. Choose based on whether your priority is eliminating vulnerabilities or eliminating milliseconds.
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