# Bundle configuration

> How playcode.config.json sets the browser editor's build - minify, keep names, tree shaking, loop protection, the language and the Solid preset.
> Source: https://playcode.io/docs/classic/bundle-configuration - last reviewed 2026-10-09.
> Ask Playcode's agent: "Turn off minify in this project's production build." It edits playcode.config.json; your next publish or download uses the new setting.

Playcode builds a static site with esbuild, in your browser. A file named `playcode.config.json`, at the root of the project, changes how: one set of options for the preview, and one for the build you publish or download.

## The production build in Settings

The three main options have switches. Open the project menu, choose **Settings…**, and find **Production build** on the **General** page: **Minify**, **Keep names** and **Tree shaking**. The page says: "Applies to published and downloaded builds, not the live preview. Stored in playcode.config.json." A switch writes the file for you.

## The file

```json
{
  "esbuildProduction": {
    "minify": true,
    "keepNames": true,
    "treeShaking": true
  },
  "esbuildDevelopment": {
    "minify": false,
    "keepNames": true,
    "treeShaking": false
  },
  "loopProtection": true
}
```

These are the values Playcode uses when the file or a key is missing.

| Key | Values | Default | What it does |
|---|---|---|---|
| `esbuildProduction.minify` | `true`, `false` | `true` | Makes the published and downloaded code smaller |
| `esbuildProduction.keepNames` | `true`, `false` | `true` | Keeps function and class names readable in the published code. Turn it off only if nothing in your code depends on names |
| `esbuildProduction.treeShaking` | `true`, `false` | `true` | Drops code that nothing imports from the published code |
| `esbuildDevelopment.minify` | `true`, `false` | `false` | The same, for the preview |
| `esbuildDevelopment.keepNames` | `true`, `false` | `true` | The same, for the preview |
| `esbuildDevelopment.treeShaking` | `true`, `false` | `false` | The same, for the preview |
| `loopProtection` | `true`, `false` | `true` | Stops a loop in the preview after 1,500 iterations. The **Loop protection** switch in **Settings** writes it |
| `language` | `javascript`, `python`, `c`, `cpp`, `go`, `sql` | `javascript` | The language the project runs |
| `preset` | `solid-js` | none | Compiles JSX for SolidJS |

## After you edit the file

| Option | When it takes effect |
|---|---|
| `esbuildProduction` | At your next publish or download |
| `esbuildDevelopment`, `loopProtection` | After you restart the preview: press Ctrl+Shift+R (Control+Shift+R on a Mac), or choose **Stop**, then **Start Preview** |

The switches in **Settings** restart the preview for you.

## Messages

| Message | Fix |
|---|---|
| "playcode.config.json is invalid. Please make sure it is correct JSON file." | The file is not valid JSON. Check its commas, quotes and braces |
| "playcode.config.json: Unknown keys: ... (typo?)" | The console names a key the editor does not know. Check its spelling |