bun.exe

Bun JavaScript Runtime

Application ProcessSafeJavaScript Runtime

CPU Usage

1-25%

Memory

50-200 MB

Location

C:\Program Files\bun

Publisher

Oven Labs

Quick Answer

bun.exe is safe. It's the Windows executable for Bun, a fast JavaScript runtime and toolchain used for server-side JS, bundling, and package management.

Is it a Virus?

✔ NO - Safe

Must be in C:\\Program Files\\bun\\bun.exe or C:\\Program Files (x86)\\bun\\bun.exe

Warning

Many bun processes may appear

Bun can spawn worker processes for bundling and dev servers; unrelated background bunx tasks can run

Can I Disable?

✔ YES

Close bun-backed servers or terminate bun.exe; disable startup items if necessary

What is bun.exe?

bun.exe is the Windows executable for Bun, a fast JavaScript runtime and toolkit designed to replace Node.js for server-side scripting, bundling, and package management. It runs as a background process and manages JS execution, TS/JS transpilation, and tooling tasks via bun commands and bunx.

Bun uses an optimized single-process model with worker threads to handle JS execution, bundling, and tooling. It implements a built-in bundler, a test runner, and a package manager to speed up dev cycles and reduce startup overhead compared with Node.js.

Quick Fact: Bun emphasizes speed with a built-in bundler and package manager, designed to reduce dev cycle times on modern JS projects.

Types of Bun Processes

Server/Runtime Process: Main bun.exe instance handling JS/TS execution
Bundling Process: Background worker for asset bundling
Tooling Process: bunx CLI tasks and package manager operations
Test/Runner Process: Tests and scripts execution context
Background Service: Watchers and background tasks for projects
Compiler/Optimizer: JIT/bytecode optimization helpers

Is bun.exe Safe?

Yes, bun.exe is safe when it's the legitimate file from Bun (Bun Labs) downloaded from official sources (bun.sh or bun distribution installers).

Is bun.exe a Virus or Malware?

The real bun.exe is NOT a virus. Malware sometimes disguises itself with similar names. Always verify the path and signature.

How to Tell if bun.exe is Legitimate or Malware

File Location: Must be in C:\Program Files\bun\bun.exe or C:\Program Files (x86)\bun\bun.exe. Any bun.exe elsewhere is suspicious.
Digital Signature: Right-click the file in Explorer → Properties → Digital Signatures. Should show an official signature from "Bun Labs" or trusted publisher.
Resource Usage: Normal bun usage varies; monitor with Task Manager. Unusually high CPU when idle is suspicious.
Behavior: Bun should run when you invoke bun or bunx. If bun.exe is active without user action, scan for malware.

Red Flags: If bun.exe is located in unusual folders, runs when you have not started Bun, has no valid digital signature, or shows unexpected network activity, scan with antivirus and verify publisher authenticity.

Why Is bun.exe Running on My PC?

bun.exe runs when you start Bun-based tooling, a server, or a watch task. It may also stay resident to speed up subsequent builds and dev commands.

Reasons it's running:

Active Bun Server: You launched a Bun-based server or API (bun run dev) and the process stays active.
Bundling or Transpiling: Bun performs bundling/transpilation for JS/TS assets, which runs as separate worker tasks.
Dev Tools and Watchers: Watch mode and automatic reload tasks keep bun.exe alive to respond quickly.
Startup or Background Service: Bun may be configured to run at system startup or as part of a dev environment bootstrap.
bunx CLI Tasks: Running bunx commands for dependencies, tests, or project tooling can keep bun.exe active in the background.

Can I Disable or Remove bun.exe?

Yes, you can disable bun.exe. It's safe to close Bun-backed servers when not in use, and you can uninstall Bun or remove it from PATH if you prefer a different runtime.

How to Stop bun.exe

End Bun Server: In the terminal where Bun is running, press Ctrl+C to stop the server.
Close Background Tasks: Use Task Manager to end bun.exe processes if needed
Prevent Startup: Disable Bun from starting automatically in your shell profile or Windows Startup items
Stop bunx Tasks: Terminate any terminal sessions running bunx commands
Uninstall Bun: Run the official uninstaller or use your package manager to remove Bun

How to Uninstall Bun

✔ Windows Settings -> Apps -> Apps & features -> Bun -> Uninstall
✔ Remove Bun's PATH entries from System Environment Variables
✔ Reinstall a preferred runtime (e.g., Node.js) if needed

Common Problems: High CPU or Memory Usage

If bun.exe is consuming excessive resources while building or serving apps:

Common Causes & Solutions

Active Dev Server or Watchers: Limit watch tasks, disable unnecessary watchers, or configure Bun to use smaller bundles.
Large Projects: Split workspaces, lazy-load modules, and prune dependencies to reduce workload.
Outdated Bun Version: Update Bun to the latest release: bun upgrade or reinstall from bun.sh
Heavy Bundles: Consider building in production mode or caching bundles to reduce runtime load.
Background Extensions or Tooling: Disable non-essential bunx tasks and external tooling that run in background.
System Hardware Limits: Increase available RAM or adjust virtualization settings to improve performance.

Quick Fixes:
1. Use bun dev with limited watchers or set BUN_DEV_SKIP_WATCHER=1 if supported
2. Check CPU usage via Task Manager: C:\\Windows\\System32\\Taskmgr.exe
3. Clear caches: Remove bun's cache directory found under C:\\Users\\Public\\bun-cache
4. Update Bun: bun upgrade or reinstall from bun.sh
5. Enable memory-saving mode if available in Bun settings

Frequently Asked Questions

Is bun.exe a virus?

No, the legitimate bun.exe from Bun Labs is not a virus. However, always verify the file is located in C:\Program Files\bun\bun.exe or C:\Program Files (x86)\bun\bun.exe and has a valid digital signature from Bun Labs.

Why is bun.exe using so much CPU?

High CPU usage typically occurs during heavy builds, bundling, or dev server activity. Use Task Manager (C:\Windows\System32\Taskmgr.exe) to identify the exact bunx process and reduce workload or optimize config.

Can I delete bun.exe?

Yes, you can uninstall Bun via Windows Settings -> Apps or by removing the Bun distribution from your shell. This will remove bun.exe and its tooling.

Can I disable bun.exe?

Yes, you can close Bun servers or disable startup entries. To stop background Bun tasks, terminate bun.exe from Task Manager.

Why is bun.exe running at startup?

Bun may be configured to start with your editor or development environment. Disable startup items in Task Manager or your shell profile to prevent automatic launch.

How do I reduce Bun's memory usage?

Close unused servers, minimize watch tasks, update Bun, and consider enabling any available memory-saving options in Bun.