Technology comparison

Bun vs Deno: APIs, performance & deployment

Choose Bun if you want a fast, Node.js-compatible runtime with a built-in bundler, package manager, and test runner, and you are comfortable with its evolving stability record. Choose Deno if you value a permission-based security model, TypeScript-first design, standards-aligned web APIs, and a polished all-in-one toolchain. Many teams can also evaluate both with a small pilot before committing, since feature maturity differs by version and workload.

Technical context and trade-offs

These differences are drawn directly from the comparison criteria below.

Runtime performance and startup. Performance claims depend on the version, workload, and hardware, so treat headline benchmarks cautiously and test with your own code.

Bun: Bun is built on JavaScriptCore and is generally optimized for fast startup and high-throughput I/O in many common workloads. It also implements its own native HTTP server and bundler, which can reduce overhead when you use its integrated toolchain. Real-world results still vary by dependency mix and workload.

Deno: Deno is built on V8 and typically offers solid, predictable performance that benefits from V8's mature optimization pipeline. Its startup times are generally competitive but can be slower than Bun in some simple script and CLI scenarios. As with any benchmark, results depend on version and workload.

Node.js and npm compatibility. Compatibility matters when migrating existing projects, and the degree of support changes between releases.

Bun: Bun aims for strong Node.js compatibility and can run many Node projects with minimal changes, including support for common built-in modules and npm packages. Some native addons, edge-case APIs, and deep framework integrations may still require adjustments depending on version. Verify your specific dependencies before migrating.

Deno: Deno has added substantial Node.js and npm compatibility, including npm package imports and Node built-in module support in recent releases. However, some Node APIs and native modules remain partially supported or behave differently, so complex legacy projects may need changes. Compatibility details vary by Deno version.

Quick verdictThe bottom line

BunDenoExplore the detailed comparison

Scores by criterion

Performance100–0 (1 criteria)

Ease of useNo direct evidence in the criteria

Ecosystem75–25 (2 criteria)

PopularityNo direct evidence in the criteria

BunDeno

Scores reflect wins in matching criteria; ties count as half a point.

Technical feature matrix

Criterion	Bun	Deno	Edge
Runtime performance and startup. Performance claims depend on the version, workload, and hardware, so treat headline benchmarks cautiously and test with your own code.	Bun is built on JavaScriptCore and is generally optimized for fast startup and high-throughput I/O in many common workloads. It also implements its own native HTTP server and bundler, which can reduce overhead when you use its integrated toolchain. Real-world results still vary by dependency mix and workload.	Deno is built on V8 and typically offers solid, predictable performance that benefits from V8's mature optimization pipeline. Its startup times are generally competitive but can be slower than Bun in some simple script and CLI scenarios. As with any benchmark, results depend on version and workload.	Bun
Node.js and npm compatibility. Compatibility matters when migrating existing projects, and the degree of support changes between releases.	Bun aims for strong Node.js compatibility and can run many Node projects with minimal changes, including support for common built-in modules and npm packages. Some native addons, edge-case APIs, and deep framework integrations may still require adjustments depending on version. Verify your specific dependencies before migrating.	Deno has added substantial Node.js and npm compatibility, including npm package imports and Node built-in module support in recent releases. However, some Node APIs and native modules remain partially supported or behave differently, so complex legacy projects may need changes. Compatibility details vary by Deno version.	Bun
Security model. Security is a design tradeoff, and neither runtime removes the need for secure coding practices and dependency review.	Bun generally follows a Node.js-style model where code has broad access to the filesystem, network, and environment unless you add sandboxing or OS-level controls. This makes it familiar but less restrictive by default. Teams should apply process isolation and dependency auditing where needed.	Deno offers a permission-based security model that restricts filesystem, network, environment, and subprocess access unless explicitly granted with flags. This can reduce risk for untrusted scripts and CLI tools. The model is not a substitute for dependency review, and permissions must be configured correctly.	Deno
Built-in tooling. Both runtimes bundle tools that can replace separate utilities, but feature depth and stability differ by version.	Bun ships with a package manager, bundler, test runner, and transpiler in a single binary, which can simplify setup for many projects. Its tools are fast and increasingly capable, though some advanced options and ecosystem integrations may lag behind dedicated tools depending on version.	Deno includes a formatter, linter, test runner, bundler, and documentation generator, all designed to work together with sensible defaults. The toolchain is cohesive and standards-oriented, though some features may be less flexible than specialized alternatives. Availability and behavior depend on the Deno version.	Comparable
TypeScript and language support. Both runtimes handle TypeScript natively, but configuration and default strictness differ.	Bun can execute TypeScript directly and supports JSX and TSX out of the box, which reduces setup for many projects. Type checking is typically handled by separate tools like tsc, and configuration behavior can differ from Deno. Exact support depends on version and project setup.	Deno treats TypeScript as a first-class language and includes a built-in type checker and strict defaults. This encourages type safety without extra configuration. Some Node-oriented TypeScript patterns may still require adjustments. Features depend on the Deno version.	Deno
Ecosystem and package management. Ecosystem maturity affects long-term maintainability, and both projects are evolving quickly.	Bun uses its own package manager and is designed to install npm packages quickly, with a large portion of the npm ecosystem generally usable. It also supports lockfiles and workspaces, though some package edge cases can appear. Compatibility should be verified per dependency and version.	Deno supports npm packages and its own URL-based module imports, and it maintains a growing third-party module registry. The ecosystem is smaller than npm but improving, and some packages may need compatibility flags or adjustments. Behavior varies by release.	Bun
Stability and production readiness. Production suitability depends on your risk tolerance, version pinning, and operational requirements.	Bun has matured significantly and is used in production by various teams, but its rapid release cadence means behavior can change between versions. Pinning versions and testing upgrades is advisable for critical services. Stability claims should be validated for your workload.	Deno has a longer track record of stable releases and a deliberate approach to standards and security. It is suitable for production services, especially where its permission model and toolchain fit the architecture. As with any runtime, pin versions and test upgrades.	Deno
Web standards and platform APIs. Alignment with web standards can reduce code changes across environments.	Bun implements many web-standard APIs such as fetch, WebSocket, and URL, alongside Node-compatible APIs. Coverage is broad and improving, but some edge behaviors may differ from browsers or other runtimes. Verify specific APIs against your target version.	Deno emphasizes web-standard APIs and aims for close alignment with browser behavior, which can make code more portable. It also provides Deno-specific APIs for system tasks. Some standards coverage may still differ by version.	Deno

When to choose each option

Choose this option if… Bun

Choose Bun when the strengths described here match your project requirements. Runtime performance and startup. Performance claims depend on the version, workload, and hardware, so treat headline benchmarks cautiously and test with your own code.: Bun is built on JavaScriptCore and is generally optimized for fast startup and high-throughput I/O in many common workloads. It also implements its own native HTTP server and bundler, which can reduce overhead when you use its integrated toolchain. Real-world results still vary by dependency mix and workload. Node.js and npm compatibility. Compatibility matters when migrating existing projects, and the degree of support changes between releases.: Bun aims for strong Node.js compatibility and can run many Node projects with minimal changes, including support for common built-in modules and npm packages. Some native addons, edge-case APIs, and deep framework integrations may still require adjustments depending on version. Verify your specific dependencies before migrating. Ecosystem and package management. Ecosystem maturity affects long-term maintainability, and both projects are evolving quickly.: Bun uses its own package manager and is designed to install npm packages quickly, with a large portion of the npm ecosystem generally usable. It also supports lockfiles and workspaces, though some package edge cases can appear. Compatibility should be verified per dependency and version.

Choose this option if… Deno

Choose Deno when the strengths described here match your project requirements. Security model. Security is a design tradeoff, and neither runtime removes the need for secure coding practices and dependency review.: Deno offers a permission-based security model that restricts filesystem, network, environment, and subprocess access unless explicitly granted with flags. This can reduce risk for untrusted scripts and CLI tools. The model is not a substitute for dependency review, and permissions must be configured correctly. TypeScript and language support. Both runtimes handle TypeScript natively, but configuration and default strictness differ.: Deno treats TypeScript as a first-class language and includes a built-in type checker and strict defaults. This encourages type safety without extra configuration. Some Node-oriented TypeScript patterns may still require adjustments. Features depend on the Deno version. Stability and production readiness. Production suitability depends on your risk tolerance, version pinning, and operational requirements.: Deno has a longer track record of stable releases and a deliberate approach to standards and security. It is suitable for production services, especially where its permission model and toolchain fit the architecture. As with any runtime, pin versions and test upgrades.

Technology role diagram

Option A

Bun

Backend

Option B

Deno

Backend

This diagram shows broad areas of use, not a complete deployment architecture.

Code examples

Bun

// hallo.ts – ausführen mit: bun run hallo.ts
const name: string = "Welt";
console.log(`Hallo, ${name}!`);

Frequently asked questions

Is Bun or Deno better for a new backend API in 2026?

Both are viable for new backend APIs, but the better fit depends on priorities. Bun offers fast startup, built-in tooling, and strong Node.js compatibility, which helps if you rely on npm packages or existing Node patterns. Deno offers a permission-based security model and a cohesive, standards-oriented toolchain, which suits teams that value explicit permissions and TypeScript-first defaults. Evaluate your dependency list and deployment environment before choosing.

Can I migrate an existing Node.js project to Bun or Deno without changes?

Migration often requires some changes, though both runtimes have improved Node.js compatibility. Bun generally aims for broad Node compatibility and can run many projects with minimal edits, but native addons and edge-case APIs may still need work. Deno supports npm packages and Node built-in modules in recent versions, yet some APIs and native modules remain partially supported. Test your specific dependencies and pin runtime versions before migrating.

Which runtime is more secure by default?

Deno is generally more restrictive by default because it uses a permission model that blocks filesystem, network, environment, and subprocess access unless explicitly granted. Bun follows a more permissive Node-style model, so code has broader access unless you add sandboxing or OS-level controls. Neither model eliminates the need for dependency review, secure coding, and least-privilege deployment.

Does Bun or Deno have better built-in tooling?

Bun bundles a package manager, bundler, test runner, and transpiler in one binary, which can simplify setup and speed up common tasks. Deno includes a formatter, linter, test runner, bundler, and documentation generator with cohesive defaults. The better choice depends on which workflows you value most, and feature depth can vary by version, so check the current documentation for your use case.

Which runtime has better npm ecosystem compatibility?

Bun generally offers broader npm compatibility and fast package installation, making it easier to use many existing Node libraries. Deno supports npm packages and URL-based imports, but its ecosystem is smaller and some packages may need compatibility flags or adjustments. Compatibility is not absolute for either runtime, so verify critical dependencies against the specific version you plan to deploy.

Are Bun and Deno suitable for production use?

Both are used in production, but they carry different risk profiles. Deno has a longer track record of stable releases and a deliberate security and standards focus, which some teams prefer for critical services. Bun has matured quickly and offers strong performance and tooling, but its rapid release cadence means you should pin versions and test upgrades. Production suitability ultimately depends on your workload, dependencies, and operational practices.

Which runtime is better for TypeScript developers?

Deno treats TypeScript as a first-class language and includes a built-in type checker with strict defaults, which can reduce configuration. Bun executes TypeScript directly and supports JSX and TSX out of the box, but type checking is typically handled by separate tools like tsc. Developers who want a batteries-included TypeScript experience may prefer Deno, while those prioritizing speed and Node compatibility may prefer Bun.

Do Bun and Deno support web-standard APIs like fetch?

Both runtimes implement common web-standard APIs such as fetch, WebSocket, and URL, which helps with code portability. Deno places a strong emphasis on close alignment with browser behavior and standards. Bun also covers many web APIs alongside Node-compatible APIs, though some edge behaviors may differ. Check the specific APIs your application uses against the runtime version you plan to use.