| browser | | [Browser](./browsers.browser.md) | Determines which browser to launch. | |
| buildId | | string | Determines which buildId to download. BuildId should uniquely identify binaries and they are used for caching. | |
| cacheDir | | string | Root path to the storage directory. | |
| platform | <code>optional</code> | [BrowserPlatform](./browsers.browserplatform.md) | Determines which platform the browser will be suited for. | **Auto-detected.** |