> ## Documentation Index
> Fetch the complete documentation index at: https://docs.jolter.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Runtimes

> Install, activate, pin, and update Node.js, Bun, and Deno with Jolter.

Jolter manages JavaScript runtimes as verified, exact-version installations under `JOLTER_HOME`.

| Runtime | Selectors                          | Provider                  |
| ------- | ---------------------------------- | ------------------------- |
| Node.js | numeric, wildcard, `latest`, `lts` | Official Node.js releases |
| Bun     | numeric, wildcard, `latest`        | Official Bun releases     |
| Deno    | numeric, wildcard, `latest`        | Official Deno releases    |

## Install a personal default

Use `jolter use` to install and activate a global fallback.

```bash theme={null}
jolter use node@lts
jolter use bun@latest
jolter use deno@2
```

The resolved exact version is stored in Jolter's active configuration. It is used outside a configured project or when a project does not declare a runtime for the command you run.

## Pin a project runtime

Run from the project root:

```bash theme={null}
jolter pin node@24
jolter sync
```

`pin` records the requirement. `sync` installs or reuses a matching exact version.

```json jolter.json theme={null}
{
  "$schema": "https://schemas.jolter.dev/project/v2/schema.json",
  "schemaVersion": 2,
  "runtime": {
    "node": "24"
  }
}
```

Only one runtime can be configured in `jolter.json`. If you pin `deno@2` after `node@24`, Jolter replaces the runtime entry and preserves tools and plugins.

## Choose selectors intentionally

| Selector                      | Use when                                                              |
| ----------------------------- | --------------------------------------------------------------------- |
| `node@lts`                    | You want a personal default that follows the current Node.js LTS line |
| `node@24` or `node@24.x`      | A project should follow a major release line                          |
| `node@24.5`                   | A project should follow a minor release line                          |
| `node@24.5.0`                 | A release job or build image must resolve exactly                     |
| `bun@latest` or `deno@latest` | You are experimenting and accept provider movement                    |

<Warning>
  Broad selectors resolve against current provider metadata. Use exact versions
  when a build must reproduce the same exact runtime over time.
</Warning>

## Compatibility files

Jolter also understands:

```text theme={null}
.node-version
.nvmrc
```

Runtime precedence is:

1. nearest ancestor `jolter.json` with a runtime;
2. nearest ancestor `.node-version`;
3. nearest ancestor `.nvmrc`;
4. global active runtime during direct shim execution.

Use `jolter.json` when you want a first-class Jolter declaration with runtime, tools, and plugins in one file.

## Verify runtime routing

```bash theme={null}
jolter doctor
jolter list
node --version
```

If the wrong runtime appears, check PATH precedence:

<CodeGroup>
  ```powershell PowerShell theme={null}
  Get-Command node -All
  ```

  ```bash Bash and Zsh theme={null}
  type -a node
  ```

  ```fish Fish theme={null}
  type -a node
  ```
</CodeGroup>

The first `node`, `bun`, or `deno` entry should be inside the Jolter shims directory.

## Runtime updates

Update the active runtime within its current major line:

```bash theme={null}
jolter update node
```

Move to a new selector:

```bash theme={null}
jolter update node@26
jolter update deno@latest
```

Project files are not changed by `update`. To change a project policy, edit or repin `jolter.json`, then run `jolter sync`.


## Related topics

- [First project](/first-project.md)
- [Configuration](/reference/configuration.md)
- [Selectors](/reference/selectors.md)
- [Automatic switching](/guides/automatic-switching.md)