Bun Online Compiler

Bun is a JavaScript runtime built from scratch with performance as the top priority. Written in Zig and using JavaScriptCore (Safari's engine) instead of V8, it starts faster and runs many workloads faster than Node.js. But speed isn't the only thing -- Bun also bundles a package manager, a bundler, a test runner, and a TypeScript transpiler into a single binary. No more juggling npm, webpack, ts-node, and jest separately.

It's designed as a drop-in replacement for Node.js. Most Node programs run on Bun without changes.

When to use a Bun online compiler

Bun is easy enough to install locally (curl -fsSL https://bun.sh/install | bash), but an online compiler is handy when:

• You want to test whether a Node.js snippet runs the same way on Bun
• You're exploring Bun-specific APIs without installing anything
• You need to share a working Bun example with someone

Bun-specific APIs in action

// Bun has built-in utilities that replace common npm packages

// Fast hashing (no crypto import needed for simple cases)
const hash = Bun.hash("hello bun");
console.log("Hash:", hash);

// Built-in SQLite (yes, it's bundled in the runtime)
// const db = new Database(":memory:");

// Performance timing
const start = Bun.nanoseconds();

// Array operations at native speed
const size = 1_000_000;
const arr = new Float64Array(size);
for (let i = 0; i < size; i++) {
    arr[i] = Math.sqrt(i);
}

const elapsed = (Bun.nanoseconds() - start) / 1_000_000;
console.log(`Computed ${size.toLocaleString()} square roots in ${elapsed.toFixed(2)}ms`);

// Bun.version and runtime info
console.log("Bun version:", Bun.version);
console.log("Revision:", Bun.revision);

// String utilities
const encoder = new TextEncoder();
const encoded = encoder.encode("Bun is fast");
console.log("Encoded bytes:", encoded.length);

Bun.nanoseconds() gives you high-resolution timing without importing perf_hooks. Bun.hash() handles common hashing without pulling in the crypto module. Bun also ships with SQLite built into the runtime, which is something no other JavaScript runtime does. These small conveniences add up -- fewer dependencies, less configuration, faster startup.

Bun on OneCompiler

OneCompiler runs your code on the Bun runtime, so you can test Bun-specific APIs and see how they differ from Node. It's a quick way to kick the tires on Bun without changing your local setup.

Try Bun here: Bun Online Compiler on OneCompiler