Bun vs Node.js

At a glance

1. Both runtimes cost nothing, so the invoice arrives as labour

Bun is MIT. Node.js is MIT. Neither sells a paid tier, so the bill is engineer-hours on three meters: the release calendar, the compatibility surface and the native-module ABI.

For teams maintaining a Node service: as of 10 November 2026, both runtimes have no price.

• Node: Node publishes a release calendar; v26 Lithium, v24 Krypton and v22 Jod are LTS.
• Bun: 1.4.0 (20 August 2026) combined the Rust rewrite with the compatibility-target move from 24.3.0 to 26.3.0 and native ABI 147.

For Bun 1.4, check whether your native addons have builds for NODE_MODULE_VERSION 147.

2. Node bills you on a date you did not choose

Node's release page reads like a work schedule:

Support window and release cycle:

1. LTS "typically guarantees that critical bugs will be fixed for a total of 30 months" (Node's wording).
2. Starting with v27, the cycle becomes annual: every major gets six months of Alpha, six of Current, then LTS.

Read it as a penalty table. It punishes the team that adopts a major and forgets it: v20 lived from 17 Apr 2023 to 24 Mar 2026, about 35 months.

If production still runs Node 20, plan a move to Node 24 or 26 LTS: Node 20 reached EOL on 24 March 2026.

3. Who should not pick Node for unbuilt TypeScript

Type stripping is on by default, stable since v25.2.0 / v24.12.0. Node executes erasable syntax without type checking; other syntax needs separate tooling.

// runs on Node 26 with no flags: every annotation here is erasable
type Host = string;
const host: Host = process.env.HOST ?? "localhost";
console.log(`binding ${host}`);

enum throws ERR_UNSUPPORTED_TYPESCRIPT_SYNTAX.

Node 26 also refuses:

• namespace with runtime code, parameter properties, import aliases: same error
• .tsx files
• paths, because tsconfig.json is ignored
• TypeScript inside node_modules
• parsing without WebAssembly: ERR_WEBASSEMBLY_NOT_SUPPORTED

This meter punishes codebases built on enums and path aliases; for them, the build step stays.

4. Bun's own node:http count leaves 415 − 403 = 12 tests failing

Bun says it plainly: "Bun is not 100% compatible with Node.js yet." Bun's own 1.4 counts against the Node 26.3.0 suite:

On node:http that is 12 ÷ 415 ≈ 2.9%, the failing 3%. Bun says 1.4 made 1,517 more Node tests pass.

The ABI tax: 1.4 moved the compatibility target from 24.3.0 to 26.3.0. NODE_MODULE_VERSION is now 147, so native addons built for Node 24 must be rebuilt.

Check required inspector APIs; module pass counts are not application coverage.

5. Who should not pick Bun: teams requiring missing APIs

Bun's compatibility docs name the gaps. Map each to a service you run:

• HTTP servers tuned for a load balancer. http.Server does not extend net.Server, the keepAlive / keepAliveInitialDelay server options are no-ops, and listen(handle) is ignored. Your keep-alive tuning silently does nothing.
• mTLS and multi-tenant TLS. node:https lacks getPeerCertificate() and getCipher() and does not support SNICallback. Retain Node if you require these APIs.
• Signing code. BoringSSL-backed node:crypto lacks ed448, x448, rsa-pss and dsa keys, has no secp256k1 curve and no chacha20-poly1305.
• APM tracing. async_hooks createHook is a stub and async ids are always 0; correlation by async id collapses.
• cluster fleets on macOS or Windows. HTTP load-balancing across workers only works on Linux, via SO_REUSEPORT.

AsyncLocalStorage context does not propagate into Worker/BroadcastChannel events in Bun.

6. Bun stays MIT after Anthropic's acquisition; check before migrating

Anthropic acquired Bun on 2 December 2025. Claude Code ships as a Bun executable (Bun's statement), and Bun's founder wrote then: "Today, Bun makes $0 in revenue." Bun stays MIT.

The acquisition changes who pays for Bun's roadmap. It does not change the licence, and it does not change the API surface you have to test.

Check today:

1. List every .node addon in the tree and whether it has a build for NODE_MODULE_VERSION 147.
2. Check required HTTP APIs, createHook, distinct async IDs, getPeerCertificate and SNICallback against Bun's gaps.
3. Write down the EOL date of the Node major running in production.

Cost arithmetic at volume

These are computed from the published unit prices, not measured. Each row prints its own formula, so you can replace our assumption with your traffic and redo it.

Decision matrix

Rows are the situation you are actually in. Pick the row before you read the pricing page again.

Code and configuration

// One binary replaces four dev dependencies:
// bun install, bun test, bun lint and bun fmt are the same executable.
import { Database } from "bun:sqlite";   // built in, no addon to compile
const db = new Database(":memory:");
db.run("create table t (id integer primary key, name text)");
// Here it breaks: a native addon built for Node 24 will not load,
// because Bun 1.4 reports NODE_MODULE_VERSION 147.

// Node 26 strips types; it does not check them or transform them.
type Host = string;
const host: Host = process.env.HOST ?? "localhost";
console.log(`binding ${host}`);
// Here it breaks: an enum is not erasable, so Node throws
// ERR_UNSUPPORTED_TYPESCRIPT_SYNTAX before your code runs.
enum Mode { Dev, Prod }

What you gain, what you give up

Migration path

Common questions

Sources & verification

Prices and limits were read from these pages on 2026-11-10. Vendor marketing claims are quoted as claims. Anything derived is arithmetic on the numbers below.

Keep reading