Interact with the clipboard

This section describes the options for writing data to the clipboard.

The Clipboard API writes arbitrary data to the clipboard from your extension. Using the API requires the permission "clipboardRead" or "clipboardWrite" in your manifest.json file. As the API is only available to Secure Contexts, it cannot be used from a content script running on http:-pages, only https:-pages.

For page scripts, the "clipboard-write" permission needs to be requested using the Web API navigator.permissions. You can check for that permission using navigator.permissions.query():

navigator.permissions.query({name: "clipboard-write"}).then((result) => {
  if (result.state === "granted" || result.state === "prompt") {
    /* write to the clipboard now */
  }
});

This function takes a string and writes it to the clipboard:

function updateClipboard(newClip) {
  navigator.clipboard.writeText(newClip).then(() => {
    /* clipboard successfully set */
  }, () => {
    /* clipboard write failed */
  });
}

The "cut" and "copy" commands of the document.execCommand() method are used to replace the clipboard's content with the selected material. These commands can be used without any special permission in short-lived event handlers for a user action (for example, a click handler).

For example, suppose you've got a popup that includes the following HTML:

<input id="input" type="text" /> <button id="copy">Copy</button>

To make the "copy" button copy the contents of the <input> element, you can use code like this:

function copy() {
  let copyText = document.querySelector("#input");
  copyText.select();
  document.execCommand("copy");
}

document.querySelector("#copy").addEventListener("click", copy);

Because the execCommand() call is inside a click event handler, you don't need any special permissions.

However, let's say that instead you trigger the copy from an alarm:

function copy() {
  let copyText = document.querySelector("#input");
  copyText.select();
  document.execCommand("copy");
}

browser.alarms.create({
  delayInMinutes: 0.1
});

browser.alarms.onAlarm.addListener(copy);

Depending on the browser, this may not work. On Firefox, it will not work, and you'll see a message like this in your console:

document.execCommand('cut'/'copy') was denied because it was not called from inside a short running user-generated event handler.

To enable this use case, you need to ask for the "clipboardWrite" permission. So: "clipboardWrite" enables you to write to the clipboard outside a short-lived event handler for a user action.

The clipboard and other APIs involved here are evolving rapidly, so there are variations among browsers in how they work.

In Chrome:

• You don't need "clipboardWrite", even to write to the clipboard outside a user-generated event handler.

In Firefox:

• navigator.clipboard.write() is not supported.

See the browser compatibility tables for more information.

This section describes the options for reading or pasting data from the clipboard.

The Clipboard API's navigator.clipboard.readText() and navigator.clipboard.read() methods let you read arbitrary text or binary data from the clipboard in secure contexts. This lets you access the data in the clipboard without pasting it into an editable element.

Once you have the "clipboard-read" permission from the Permissions API, you can read from the clipboard easily. For example, this snippet of code fetches the text from the clipboard and replaces the contents of the element with the ID "outbox" with that text.

navigator.clipboard.readText().then((clipText) =>
  document.getElementById("outbox").innerText = clipText);

To use document.execCommand("paste") your extension needs the "clipboardRead" permission. This is the case even if you're using the "paste" command from within a user-generated event handler, such as click or keypress.

Consider HTML that includes something like this:

<textarea id="output"></textarea> <button id="paste">Paste</button>

To set the content of the <textarea> element with the ID "output" from the clipboard when the user clicks the "paste" <button>, you can use code like this:

function paste() {
  let pasteText = document.querySelector("#output");
  pasteText.focus();
  document.execCommand("paste");
  console.log(pasteText.textContent);
}

document.querySelector("#paste").addEventListener("click", paste);

Firefox supports the "clipboardRead" permission from version 54 but only supports pasting into elements in content editable mode, which for content scripts only works with a <textarea>. For background scripts, any element can be set to content editable mode.

• Clipboard API
• Permissions API
• Make content editable