Toggles Reader Mode for the given tab.

This function toggles Reader Mode for the given tab. It takes a tab ID as a parameter: if this is omitted, the currently active tab is toggled.

This is an asynchronous function that returns a Promise.

Reader Mode, also known as Reader View, is a browser feature that makes it easier for the user to focus on an article by:

• hiding non-essential page elements like sidebars, footers, and ads
• changing the page's text size, contrast and layout for better readability.

Reader Mode is useful specifically for articles: meaning, pages that have a body of text content as their main feature. Pages that don't have an identifiable article are not eligible for display in Reader Mode. To find out whether a page is an article, check the isArticle property of tabs.Tab.

To find out whether a tab is already in Reader Mode, check the isInReaderMode property of tabs.Tab. To track tabs changing into or out of Reader Mode, you'll need to keep track of the current state of all tabs, and check when isInReaderMode changes:

function handleUpdated(tabId, changeInfo, tabInfo) {
  if (changeInfo.status === "complete") {
    console.log(`Tab ${tabId} reader mode: ${tabInfo.isInReaderMode}`);
  }
}

browser.tabs.onUpdated.addListener(handleUpdated);