A BrowserSetting object whose underlying value is a boolean.

This property sets the configuration setting browser.zoom.siteSpecific, which controls how zoom settings are applied to sites and tabs.

If browser.zoom.siteSpecific is true, zoom operations apply to all pages from the same site so that:

  • when a page loads, if there is a zoom level for that site it is applied to the page otherwise the global default zoom level is applied.
  • when the zoom level for a page changes, the zoom levels of other pages from the site in other tabs are also changed.

If browser.zoom.siteSpecific is set false, zoom operations apply to the active tab only so that:

  • when a new tab opens, the global default zoom level is applied.
  • when the zoom level in a tab changes, it persists across page loads and does not affect the zoom level in any other tab.

When Firefox is installed, browser.zoom.siteSpecific is true.

If privacy.websites.resistFingerprinting is true, this setting has no effect and zoom is set on a per-tab basis.

Browser compatibility

BCD tables only load in the browser


Set the setting to false:

function logResult(result) {
  console.log(`Setting was modified: ${result}`);

browser.browserSettings.zoomSiteSpecific.set({ value: false }).then(logResult);