Bun vs Node.js Runtime Performance 2025 Benchmarks

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You’re trying to run performance benchmarks between Bun and Node.js, but something’s not working right. Maybe the tests are crashing, giving wildly inconsistent results, or your benchmarking setup seems broken. This comparison matters because choosing the wrong runtime in 2025 could seriously impact your application’s speed and resource usage.

Step-by-Step Fixes

Step 1: Verify Both Runtimes Are Properly Installed

First, let’s make sure both Bun and Node.js are actually installed and working. Open your terminal and run these commands:

“`bash

node –version

bun –version

“`

If either command fails, you’ll need to install the missing runtime. For Node.js, grab the latest LTS version from nodejs.org. For Bun, run this command:

“`bash

curl -fsSL https://bun.sh/install | bash

“`

Step 2: Clear All Caches and Previous Test Data

Old benchmark data can mess with your results. Clean everything up:

“`bash

rm -rf node_modules

rm -rf .bun

rm -rf benchmark-results/

bun install –force

npm cache clean –force

“`

This ensures you’re starting fresh without any cached modules affecting your tests.

Step 3: Check Your Benchmark Code for Common Mistakes

Your benchmark script might have issues. Here’s a basic template that works reliably:

“`javascript

// benchmark.js

const iterations = 100000;

console.time(‘Test Duration’);

for (let i = 0; i < iterations; i++) {

// Your test code here

const result = Math.sqrt(i) * Math.random();

}

console.timeEnd(‘Test Duration’);

“`

Make sure you’re not accidentally including setup time in your measurements or using different test parameters for each runtime.

Step 4: Run Tests in Isolation

Background processes can skew results. Close all unnecessary applications, then run each benchmark separately:

“`bash

For Node.js

node benchmark.js

Wait 30 seconds, then:

For Bun

bun run benchmark.js

“`

Run each test at least three times and average the results. Single runs can be misleading.

Step 5: Use Professional Benchmarking Tools

If manual testing isn’t working, try established benchmarking frameworks:

“`bash

npm install -g hyperfine

hyperfine ‘node benchmark.js’ ‘bun run benchmark.js’

“`

Hyperfine automatically handles warm-up runs, statistical analysis, and gives you clean comparison data.

Step 6: Monitor System Resources During Tests

Open Activity Monitor on macOS, Task Manager on Windows, or run `htop` on Linux while benchmarking. If CPU usage hits 100% or RAM is maxed out, your results won’t be accurate. Close other applications or upgrade your system resources.

Likely Causes

Cause #1: Version Mismatch Between Environments

You might be comparing an outdated Node.js version against the latest Bun release, which isn’t fair. Bun updates frequently with performance improvements, while Node.js has a slower release cycle.

Check your versions match current 2025 standards. Node.js should be at least v22.x, and Bun should be 1.1.x or higher. Update both to their latest stable versions:

“`bash

Update Node.js using nvm

nvm install node –latest-npm

Update Bun

bun upgrade

“`

Cause #2: Incompatible Benchmark Code

Some JavaScript features work differently between runtimes. Bun implements certain APIs differently than Node.js for performance reasons. Your benchmark might be hitting these differences.

Common incompatibilities include:

  • Buffer operations
  • Crypto functions
  • File system APIs
  • HTTP server implementations

Test with simple, compatible code first. If basic math operations benchmark correctly but complex operations fail, you’ve found the issue. Rewrite your benchmarks using only shared, standard JavaScript features.

Cause #3: Operating System Interference

Windows Defender, macOS Gatekeeper, or Linux security modules might be slowing down one runtime more than the other. Bun, being newer, sometimes triggers more security scans.

Temporarily disable real-time protection while benchmarking (remember to re-enable it afterward). On macOS, you might need to allow both executables in System Preferences > Security & Privacy. Linux users should check if SELinux or AppArmor is interfering.

When to Call a Technician

If you’ve tried all these steps and still can’t get reliable benchmarks, it’s time for expert help. Contact a technician when:

  • Your benchmarks crash with segmentation faults or core dumps
  • Results vary by more than 500% between runs
  • One runtime consistently shows 0ms execution time (indicating the test isn’t running)
  • You’re benchmarking for production deployment and need guaranteed accuracy

A professional can set up isolated testing environments, use specialized profiling tools, and identify hardware-specific issues affecting your results.

Copy-Paste Prompt for AI Help

If you need more specific help, copy this prompt:

“I’m trying to benchmark Bun vs Node.js performance in 2025 but getting inconsistent results. My Node version is [YOUR VERSION], Bun version is [YOUR VERSION], running on [YOUR OS]. The benchmark code tests [DESCRIBE WHAT YOU’RE TESTING]. Node.js shows [X]ms average, Bun shows [Y]ms average, but results vary by [Z]%. What specific steps should I take to get accurate, reproducible benchmark results?”

Remember, runtime performance depends heavily on your specific use case. What’s faster for one application might be slower for another. Focus on benchmarking your actual workload, not synthetic tests.

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