bytemofan / clipboard-polyfill

:clipboard: Sane copying on the web, with maximum browser compatibility.

clipboard-polyfill

Make copying on the web as easy as:

clipboard.writeText("hello world");

As of October 2017, this library is a polyfill for the modern Promise-based asynchronous clipboard API.

Why clipboard-polyfill?

Browsers have implemented several clipboard APIs over time, and writing to the clipboard without triggering bugs in various old and current browsers is fairly tricky. In every browser that supports copying to the clipboard in some way, clipboard-polyfill attempts to act as close as possible to the async clipboard API. (Read to the end of this document for all the limitations.)

Note: If you only need to copy text and want a super simple polyfill that gets you 80% of the way, consider using this gist.

Usage

Get the source using one of the following:

• Download build/clipboard-polyfill.js and include it using a <script> tag.
• npm install clipboard-polyfill and import as clipboard.

Plain Text

Copy text to the clipboard (all modern browsers):

clipboard.writeText("This text is plain.");

Read text from the clipboard (IE 9-11 and Chrome 65+):

clipboard.readText().then(console.log, console.error);

Caveats:

• Browsers may require a user gesture or user permission to access the clipboard. In particular, you should write text only in response to an event listener, e.g. a button click listener.
• Reading fails if the clipboard does not contain text/plain data.

Other Data Types (e.g. HTML)

Write (all modern browsers):

var dt = new clipboard.DT();
dt.setData("text/plain", "Fallback markup text.");
dt.setData("text/html", "<i>Markup</i> <b>text</b>.");
clipboard.write(dt);

Read (IE 9-11, Chrome 65+):

// The success callback receives a clipboard.DT object.
clipboard.read().then(console.log, console.error);

Caveats:

• Currently, text/plain and text/html are the only data types that can be written to the clipboard across most browsers.
• Unsupported data types will be silently dropped. In general, it is not possible to tell which data types will be dropped.
• This part of the clipboard API is still under active discussion, and may change.
• Currently, reading will only return the text/plain data type, if it is on the clipboard.

Interface

clipboard {
  static write:     (data: clipboard.DT)  => Promise<void>
  static writeText: (s: string) => Promise<void>
  static read:      () => Promise<clipboard.DT>
  static readText:  () => Promise<string>
  static suppressWarnings: () => void
}

clipboard.DT {
  constructor()
  setData: (type: string, value: string): void
  getData: (type: string): string | undefined
}

A note on clipboard.DT

The asynchronous clipboard API works like this:

var dt = new DataTransfer();
dt.setData("text/plain", "plain text");
navigator.clipboard.write(dt);

Ideally, clipboard-polyfill would take a DataTransfer, so that the code above works verbatim when you replace navigator.clipboard with clipboard. However, the DataTransfer constructor cannot be called in most browsers. Thus, this library uses a light-weight alternative to DataTransfer, exposed as clipboard.DT:

var dt = new clipboard.DT();
dt.setData("text/plain", "plain text");
clipboard.write(dt);

This is way too complicated!

Try this gist for a simpler solution.

Can I use it?

• Chrome 42+
• Firefox 41+
• Opera 29+
• Internet Explorer 9+ (text only)
• Edge
• Desktop Safari 10+
• iOS Safari 10+ (text only)

clipboard-polyfill uses a variety of heuristics to get around compatibility bugs. Please let us know if you are running into compatibility issues with any of the browsers listed above.

Limitations

• In Microsoft Edge, it seems to be impossible to detect whether the copy action actually succeeded (Edge Bug #14110451, Edge Bug #14080262). clipboard-polyfill will always call resolve() in Edge.
• In Microsoft Edge, only the last data type you specify is copied to the clipboard (Edge Bug #14080506).
  • DataTransfer and clipbard.DT keep track of the order in which you set items. If you care which data type Edge copies, call setData() with that data type last.
• On iOS Safari (WebKit Bug #177715) and Internet Explorer, only text copying works.
  • On iOS Safari, clipboard-polyfill needs to use the DOM to copy, so the text will be copied as rich text. clipboard-polyfill attempts to use shadow DOM in order to avoid some of the page formatting (e.g. background color) from affecting the copied text. However, such formatting might be copied if shadow DOM is not available.
  • In other browsers, writing copy data that does not include the text/plain data type will succeed, but also show a console warning:

clipboard.write() was called without a text/plain data type. On some platforms, this may result in an empty clipboard. Call clipboard.suppressWarnings() to suppress this warning.

• clipboard-polyfill attemps to avoid changing the document selection or modifying the DOM. However, clipboard-polyfill will automatically fall back to using such techniques if needed:
  • On iOS Safari, the user's current selection will be cleared. This should not happen on other platforms unless there are unanticipated bugs. (Please file an issue if you observe this!)
  • On iOS Safari and under certain conditions on desktop Safari (WebKit Bug #177715), clipbard-polyfill needs to add a temporary element to the DOM. This will trigger a mutation observer if you have attached one to document.body. Please file an issue if you'd like to discuss how to detect temporary elements added by clipboard-polyfill.
• read() currently only works in Internet Explorer.
  • Internet Explorer can only read text/plain values from the clipboard.
• Internet Explorer does not have a native Promise implementation, so the standalone build file for clipboard-polyfill also includes stefanpenner's es6-promise polyfill. This adds significant size to the build. Please file an issue if you're interested in a minimal build without Internet Explorer support.
• Microsoft Edge (at least EdgeHTML version <17) does not write text/html to the clipboard using the Windows CF_HTML clipboard format (Edge Bug #14372529), which prevents other programs (including other browsers) from recognizing the copied HTML data (issue #73). clipboard-polyfill currently does not attempt to work around this issue.