Option Fields

Last updated 2026-10-21

Every field of browser.Option, the value used when it is left at its zero value, and how fields interact.

Fields

Field	Type	When unset	Notes
`IdleWait`	`time.Duration`	`2s`	Cap for each settle, `SettleJS` and consent evaluation; the DOM stability window is `min(400ms, IdleWait)`
`MaxLength`	`int`	`1048576` (`1 << 20`)	Markdown output is cut to this many bytes, which can split a multi-byte character; a negative value disables truncation; ignored by `TypeHTML` and `TypeJSON`
`UserAgent`	`string`	`DefaultUserAgent`	Also part of the browser cache key
`KeepLinks`	`bool`	`false`	Keep links, images and `nav` / `header` / `footer` / `aside` in converted output
`StealthJS`	`string`	embedded `stealth.js`	Injected with `EvalOnNewDocument`; replaces the default, an empty string restores it, see Anti-Detection
`SettleJS`	`string`	embedded `listener.js`	Evaluated once after the DOM settles; an empty string restores the default
`Viewport`	`*Viewport`	`1280 × 960`	`DeviceScaleFactor` 0 is treated as 1
`SameSession`	`bool`	`false`	Temporary profile with local Chrome cookies, see Cookie Sessions
`Headless`	`bool`	`false`	Forces headless with no headed retry
`Visible`	`bool`	`false`	Goes headed directly with no retry when a GUI is available; without a GUI it falls back to headless first. Ignored when `Headless` is true, see Fetch Routing
`Profile`	`string`	`"Default"`	Chrome profile directory name, used only with `SameSession`
`Type`	`int`	`TypeMarkdown`	`TypeMarkdown`, `TypeHTML` or `TypeJSON`, see Output Formats
`ScrollCount`	`int`	`3`	A negative value means no scrolling

Fetch copies the Option before filling defaults, so the value you pass is never modified and can be reused across calls.

Viewport

type Viewport struct {
	Width             int
	Height            int
	DeviceScaleFactor float64
}

Field interactions

Combination	Effect
`Headless: true` + session domain	Headless wins; the session domain list is ignored
`Headless: true` + `Visible: true`	Headless wins; `Visible` is ignored
`Visible: true` without a GUI	Same as unset: headless first, headed retry not possible
`Headless: true` + `SameSession: true`	A headless browser on the temporary cookie profile
`SameSession: false` + `Profile`	`Profile` has no effect
`ScrollCount: 0`	Treated as unset, so 3 passes; use `-1` to disable
`IdleWait` below 400ms	The DOM stability window shrinks to `IdleWait`

Example

result, err := browser.Fetch(ctx, href, 45*time.Second, &browser.Option{
	Type:        browser.TypeMarkdown,
	KeepLinks:   true,
	ScrollCount: 5,
	IdleWait:    3 * time.Second,
	Viewport:    &browser.Viewport{Width: 1440, Height: 2000},
})