Bun vs Node.js vs Deno: Which JavaScript Runtime to Choose

For most of JavaScript history, Node.js was the only serious server-side runtime. In 2022 Deno reached 1.0 with a focus on security and modern defaults. In 2023 Bun launched with a focus on raw performance and an all-in-one toolchain. By 2026, all three are production-ready and actively developed. The choice between them is a real decision for new projects.

All three run JavaScript and TypeScript on the server. All three implement a Web-compatible API surface (fetch, WebCrypto, URL, etc.). The differences are in performance, ecosystem compatibility, built-in tooling, security model, and maturity of the surrounding ecosystem. This comparison covers each dimension so you can make an informed choice.

Node.js is the oldest and most widely deployed JavaScript runtime. npm has over 2.5 million packages. Every major framework — Express, Fastify, NestJS, Next.js, Nuxt, Remix — runs on Node.js. The ecosystem assumption is Node.js: documentation examples, Stack Overflow answers, and third-party integrations are all written with Node.js in mind.

Node.js runs on V8 (the same JavaScript engine as Chrome) and has excellent performance for I/O-bound workloads. It does not have built-in TypeScript support — you need ts-node, tsx, or a build step. The toolchain is fragmented: separate tools for bundling (webpack, esbuild, Rollup), testing (Jest, Vitest), and formatting (Prettier, ESLint). This fragmentation is a real cost in setup time. Node.js 20+ has a built-in test runner and the --experimental-strip-types flag for running TypeScript directly, which narrows the toolchain gap.

Deno 2.0 (released October 2024) dramatically improved npm compatibility — you can import npm packages directly with npm: specifiers and run most Node.js code without modification. Deno runs TypeScript natively without a build step. It has a built-in formatter (deno fmt), linter (deno lint), test runner (deno test), bundler (deno bundle), and documentation generator.

The defining Deno feature is its security model. By default Deno scripts cannot read files, write files, access the network, or read environment variables without explicit permission flags: --allow-read, --allow-net, --allow-env. This makes Deno safer for running untrusted code and encourages explicit capability declarations. The trade-off is friction when running third-party packages that need permissions you did not anticipate.

Bun is built on JavaScriptCore (the Safari JavaScript engine) and written in Zig. It is significantly faster than Node.js and Deno on startup time and raw throughput benchmarks: Bun HTTP server benchmarks show 2-4x higher requests per second than Node.js for simple servers. Bun installs npm packages 20-30x faster than npm due to a binary lockfile and parallel downloads.

Bun runs TypeScript natively without a build step. It includes a bundler, test runner, package manager, and task runner — replacing esbuild, Jest, npm, and shell scripts with a single binary. npm compatibility is high: most Node.js packages work without modification. The main caveat is that Bun is newer and has had compatibility issues with packages that use Node.js internals deeply. Stability has improved significantly but it is still less battle-tested than Node.js in long-running production deployments.

Startup time: Bun starts in 5-15ms, Deno in 20-50ms, Node.js in 80-150ms for a simple script. This matters for CLI tools and serverless functions with cold starts. For long-running servers, startup time is irrelevant.

HTTP throughput: Bun HTTP server benchmarks at 100,000-200,000 requests/second for a simple hello-world server. Node.js with Fastify benchmarks at 60,000-100,000 requests/second. Real-world application performance is much closer because the bottleneck is almost always I/O (database, external API calls), not the runtime. Package installation: Bun install is 10-30x faster than npm install. This matters in CI/CD where npm install is a significant time cost.

Choose Node.js for production applications with complex third-party dependencies, for projects using a framework with deep Node.js integration (NestJS, Next.js server, Prisma), or for teams where hiring and documentation access to Node.js knowledge matters. Node.js is also the correct choice when you need the most mature ecosystem and maximum operational certainty.

Choose Bun for new projects where you want the fastest possible development iteration (quick install, native TypeScript), for CLI tools where startup time matters, and for high-throughput APIs where Bun raw performance provides a meaningful advantage. Choose Deno for security-sensitive scripts, for Edge runtime deployments (Deno Deploy is a first-class platform), for projects where the built-in toolchain all-in-one approach and Web API compatibility are priorities, and when you value the permission system for explicit capability control.