bun-types/docs/guides/util/detect-bun.mdx

Type definitions and documentation for Bun, an incredibly fast JavaScript runtime

---
title: Detect when code is executed with Bun
sidebarTitle: Detect Bun
mode: center
---

The recommended way to detect when code is being executed with Bun is to check `process.versions.bun`. This works in both JavaScript and TypeScript without requiring any additional type definitions.

```ts
if (process.versions.bun) {
  // this code will only run when the file is run with Bun
}
```

---

Alternatively, you can check for the existence of the `Bun` global. This is similar to how you'd check for the existence of the `window` variable to detect when code is being executed in a browser.

<Note>
  This approach will result in a type error in TypeScript unless `@types/bun` is installed. You can install it with `bun
  add -d @types/bun`.
</Note>

```ts
if (typeof Bun !== "undefined") {
  // this code will only run when the file is run with Bun
}
```