action.setBadgeText()

browser.action.setBadgeText(
  details // object
)

This API is also available as chrome.action.setBadgeText().

details

An object with the following properties:

text

string or null. Any number of characters can be passed, but only about four can fit in the space.

Use an empty string - "" - if you don't want any badge.

If a tabId is specified, null removes the tab-specific badge text so that the tab inherits the global badge text. Otherwise it reverts the global badge text to "".

If a windowId is specified, null removes the window-specific badge text so that the tab inherits the global badge text. Otherwise it reverts the global badge text to "".

tabId Optional

integer. Set the badge text only for the given tab. The text is reset when the user navigates this tab to a new page.

windowId Optional

integer. Set the badge text for the given window.

• If windowId and tabId are both supplied, the function fails.
• If windowId and tabId are both omitted, the global badge is set.

Add a badge indicating how many times the user clicked the button:

let clicks = 0;

function increment() {
  browser.action.setBadgeText({ text: (++clicks).toString() });
}

browser.action.onClicked.addListener(increment);