Clipboard: write() method

The write() method of the {{domxref("Clipboard")}} interface writes arbitrary {{domxref("ClipboardItem")}} data such as images and text to the clipboard, fulfilling the returned {{jsxref("Promise")}} on completion. This can be used to implement cut and copy functionality.

The method can in theory write arbitrary data (unlike {{domxref("Clipboard.writeText", "writeText()")}}, which can only write text). Browsers commonly support writing text, HTML, and PNG image data.

Syntax

js-nolint

write(data)

Parameters

data
- : An array of {{domxref("ClipboardItem")}} objects containing data to be written to the clipboard.

Return value

A {{jsxref("Promise")}} which is resolved when the data has been written to the clipboard. Note that if the underlying OS does not support multiple native clipboard items on the system clipboard, then only the first {{domxref("ClipboardItem")}} in the array is written.

The promise is rejected if the clipboard is unable to write to the clipboard.

Exceptions

NotAllowedError {{domxref("DOMException")}}
- : Thrown if writing to the clipboard is not allowed.

Security considerations

Writing to the clipboard can only be done in a secure context.

Additional security requirements are covered in the Security consideration section of the API overview topic.

Examples

Write text to the clipboard

This example function replaces the current contents of the clipboard with a specified string when a button is pressed. Note that for this particular case, you could just as readily use Clipboard.writeText().

button.addEventListener("click", () => setClipboard("<empty clipboard>"));

async function setClipboard(text) {
  const type = "text/plain";
  const clipboardItemData = {
    [type]: text,
  };
  const clipboardItem = new ClipboardItem(clipboardItemData);
  await navigator.clipboard.write([clipboardItem]);
}

The setClipboard() function specifies a "text/plain" MIME type in the type constant, then specifies a clipboardItemData object with a single property — its key is the MIME type, and its value is the passed in text that we want to write to the clipboard. We then construct a new {{domxref("ClipboardItem")}} object into which the clipboardItemData object is passed.

Finally, write() is called with await to write the data to the clipboard.

Write canvas contents to the clipboard

This example draws a blue rectangle to the canvas. You can click the rectangle to copy the content of the canvas into the clipboard as an image, and then select another element and paste in the content from the clipboard.

HTML

The HTML just defines our <canvas> element and the <div> element with id target where the canvas image will be pasted.

html

<canvas id="canvas" width="100" height="100"></canvas>

<div id="target">Paste here.</div>

html

<pre id="log"></pre>

css

#log {
  height: 60px;
  overflow: scroll;
  padding: 0.5rem;
  border: 1px solid black;
}

const logElement = document.querySelector("#log");
function log(text) {
  logElement.innerText = `${logElement.innerText}${text}\n`;
  logElement.scrollTop = logElement.scrollHeight;
}

JavaScript

First we define an async function to copy a canvas to a blob. This wraps the old callback-style {{domxref("HTMLCanvasElement.toBlob()")}} method into the more intuitive Promise based function.

// Async/await method replacing toBlob() callback
async function getBlobFromCanvas(canvas) {
  return new Promise((resolve, reject) => {
    canvas.toBlob((blob) => {
      if (blob) {
        resolve(blob);
      } else {
        reject(new Error("Canvas toBlob failed"));
      }
    });
  });
}

Next we set up our canvas and add an event listener for the click event.

When you click the blue rectangle, the canvas displaying the rectangle is copied into a blob, and then the blob is added to a ClipboardItem and then written to the clipboard.

const canvas = document.getElementById("canvas");

// Set up canvas
const ctx = canvas.getContext("2d");
ctx.fillStyle = "cornflowerblue";
ctx.fillRect(0, 0, 100, 100);

canvas.addEventListener("click", copyCanvasContentsToClipboard);
const target = document.getElementById("target");

async function copyCanvasContentsToClipboard() {
  // Copy canvas to blob
  try {
    const blob = await getBlobFromCanvas(canvas);
    // Create ClipboardItem with blob and it's type, and add to an array
    const data = [new ClipboardItem({ [blob.type]: blob })];
    // Write the data to the clipboard
    await navigator.clipboard.write(data);
    log("Copied");
  } catch (error) {
    log(error);
  }
}

Note that if you are fetching a less-common file type or a resource that you don't know the type in advance, you may want to use {{domxref("ClipboardItem.supports_static", "ClipboardItem.supports()")}} to check if the file type is supported, and provide a good error message to the user in case it isn't.

We then define an event listener for paste events on then element where we want to display the clipboard contents as an image. The FileReader API allows us to read the blob using the readAsDataUrl method and create an `` element with the canvas contents:

target.addEventListener("paste", (event) => {
  const items = (event.clipboardData || window.clipboardData).items;
  const blob = items[0].getAsFile();
  const reader = new FileReader();

  reader.addEventListener("load", (event) => {
    const img = new Image();
    img.src = event.target.result;
    target.appendChild(img);
  });

  reader.readAsDataURL(blob);
});

css

body {
  font-family: sans-serif;
}
#target {
  border: 2px solid;
  padding: 1rem;
  height: 150px;
}
img {
  margin: 0.5rem;
}

Result

The result is shown below. First click on the blue square, and then select the text "Paste here" and use your OS-specific keyboard combinations to paste from the clipboard (such as Ctrl+V on Windows).

{{embedlivesample("write_canvas_contents_to_the_clipboard", "", "420", "", "", "", "clipboard-write")}}