# Migrate from Node.js

> Find and rewrite Node.js APIs that have a Bun equivalent with bun n2b, and migrate a project with bun migrate

`bun n2b` scans a project for Node.js APIs that have a faster or simpler Bun equivalent, such as `fs.readFile` for `Bun.file().text()` or `child_process` for `Bun.spawn`, and can rewrite them. `bun migrate` moves a whole Node.js project to Bun.

```bash terminal icon="terminal"
bun n2b
```

Each finding has a rule, a severity, a message and, when one exists, the replacement code.

## Rewrite code

```bash terminal icon="terminal"
# apply the safe rewrites
bun n2b --fix

# also apply the rewrites that change behavior in edge cases
bun n2b --aggressive
```

## Reports

```bash terminal icon="terminal"
bun n2b --report=json > n2b.json
bun n2b --report=jsonl
```

[`bun lint`](https://bun.aphrody.com/docs/runtime/lint) runs the same rules beside oxlint and merges the findings into one report, so most projects only need `bun lint` and `bun lint --fix`.

## Migrate a project

`bun migrate` applies every n2b rewrite, converts pnpm workspaces, catalogs and overrides to `package.json`, removes the other lockfiles and runs `bun install`.

```bash terminal icon="terminal"
# print the migration plan and change nothing
bun migrate --dry-run

bun migrate
```

`bun migrate` is the same as `bun n2b migrate`.

## How n2b is installed

n2b is not part of the `bun` binary. The first `bun n2b`, `bun migrate` or `bun lint` downloads a pinned version of `@aphrody/bun-plugin-n2b` with [`bun x`](https://bun.aphrody.com/docs/pm/bunx) and caches it.

`bun n2b --help` lists every n2b command and flag.

If `package.json` has an `n2b` or `migrate` script, `bun n2b` or `bun migrate` runs that script. Inside the script, the name is the command.