Deno 2 vs Bun: A Practical Comparison

Deno 2 and Bun have reached a level of maturity that invites serious comparison. Deno 2 focuses on security, standards alignment, and a seamless bridge to the Node and npm world, while Bun pursues raw speed and an all-in-one toolkit philosophy. Benchmarks place Bun at the front for throughput, yet Deno shows competitive latency and a richer permissions model. Choosing between them now hinges less on novelty and more on whether your project values top-end performance or a security-first, standards-focused developer experience.

Why a comparison matters in 2025

Both runtimes now power production workloads, and both offer credible Node compatibility, making the decision consequential for new projects. Deno Land Inc. and Oven, the companies behind the runtimes, operate out of San Francisco /ˌsæn frənˈsɪskoʊ/, yet they approach JavaScript's future from different angles, so documenting their trade-offs helps developers avoid costly rewrites later.

Architecture and core philosophies

Engine choices and implementation languages

Deno embeds Google's V8 and is written primarily in Rust, reflecting its creators' goal of aligning server JavaScript with browser standards. Bun is built in Zig and runs JavaScriptCore, the engine behind Safari. This choice allows tight control over memory and fast startup times, giving Bun its trademark speed.

Standard library and built-in tooling

Deno arrives with a formatter, linter, test runner, bundler, and task system that share cohesive CLI ergonomics. Recent releases added a lockfile v4 format, OpenTelemetry support, and a pluggable lint API. Bun bundles a transpiler, test runner, router, SQL client, and its own installer. The 1.2 series improved build speeds by up to sixty percent on macOS and brought hot reloading and code-signable single-file executables.

Compatibility with Node and npm

Deno 2 removed many of the browser-only globals that had hindered npm packages and now understands package.json, so most Node libraries work after a simple npm: import specifier. Bun targets near-complete Node compatibility, running the Node test-suite on every commit and shipping an almost drop-in bun install replacement for npm.

Performance in the real world

Independent HTTP benchmarks show Bun exceeding fifty-two thousand requests per second with Express-style servers, doubling Deno's throughput and quadrupling Node's. Other tests that stress concurrency report Deno edging ahead in sustained request handling, illustrating how engine choice, not just raw execution speed, shapes results. Bun 1.2.4 further lowered build times and introduced a dedicated I/O thread pool, while Deno's binary size and language-server latency continue to trend downward in their public dashboards.

Security posture

Deno enforces explicit permissions for file, network, and environment access, so a script cannot read the file-system unless you allow it. The model remains opt-in and isolates third-party code by default. Bun exposes the full host by default, mirroring Node's permissive model, though containerization and forthcoming policy files mitigate some risks. Community demand for a tighter sandbox is growing but still experimental.

Developer experience

Cold start times shape CLI and serverless work. Bun starts almost instantly, making it attractive for short-lived commands and edge functions. Deno's internal caching and the new lockfile shrink install footprints, giving TypeScript projects predictable builds without a node_modules directory. Memory usage improved in Bun 1.2.2, dropping idle consumption by up to thirty percent, while Deno 2.2's linter plugin system lets teams encode style rules without external tooling.

Ecosystem and community momentum

Blog statistics and surveys still show Node dominating, but Bun's GitHub releases land every few weeks and its Discord grows steadily. Deno's JSR registry encourages publish-once, run-anywhere modules that work in the browser, Deno, and Node, signaling a broader standards push. Community articles converge on three roles: choose Bun for greenfield performance, choose Deno for security-sensitive services, and keep Node for mature enterprise ecosystems.

When Deno 2 feels like the right fit

Pick Deno if your team values built-in TypeScript, a granular permission model, and first-class tooling aligned with web standards. The runtime thrives in internal platforms where predictable builds, auditability, and strong linting outweigh peak throughput. Long-term, JSR promises a smoother isomorphic story for libraries.

When Bun 1.2 shines

Choose Bun when every millisecond matters, such as low-latency APIs, game servers, or developer tooling where startup pause feels intrusive. Its bundled transpiler, router, and test runner shrink dependencies and its speed helps tasks like static builds finish sooner. Ongoing Node parity and frequent releases suggest a rapidly evolving but ambitious ecosystem.

Looking ahead

Deno's roadmap highlights deeper npm compatibility and faster language-server performance, while Bun's GitHub issue tracker lists Windows stability and Node API coverage as active work. Both teams iterate weekly, so expect today's edge cases to vanish quickly.

Final reflections

Deno 2 and Bun no longer feel experimental. They represent distinct philosophies that converge on practical goals: simpler tooling, lighter installs, and a smoother path from local code to global deployment. Performance charts are persuasive, yet day-to-day ergonomics, security needs, and team familiarity will decide which runtime feels like home.