Firefox 63 is rolling into Beta and it’s absolutely loaded with new features for extensions. There are some important new API, some major enhancements to existing API, and a large collection of miscellaneous improvements and bug fixes. All told, this is the biggest upgrade to the WebExtensions API since the release of Firefox Quantum.

An upgrade this large would not have been possible in a single release without the hard work of our Mozilla community. Volunteer contributors landed over 25% of all the features and bug fixes for WebExtensions in Firefox 63, a truly remarkable effort. We are humbled and grateful for your support of Firefox and the open web. Thank you.

Note: due to the large volume of changes in this release, the MDN documentation is still catching up. I’ve tried to link to MDN where possible, and more information will appear in the weeks leading up to the public release of Firefox 63.

Less Kludgy Clipboard Access

A consistent source of irritation for developers since the WebExtensions API was introduced is that clipboard access is not optimal. Having to use execCommand() to cut, copy and paste always felt like a workaround rather than a valid way to interact with the clipboard.

That all changes in Firefox 63. Starting with this release, parts of the official W3C draft spec for asynchronous clipboard API is now available to extensions. When using the clipboard, extensions can use standard the WebAPI to read and write to the clipboard using navigator.clipboard.readText() and navigator.clipboard.writeText(). A couple of things to note:

clipboard.writeText is available to secure contexts and extensions, without requiring any permissions, as long as it is used in a user-initiated event callback. Extensions can request the clipboardWrite permission if they want to use clipboard.writeText outside of a user-initiated event callback. This preserves the same use conditions as document.execCommand(“copy”).

clipboard.readText is available to extensions only and requires the clipboardRead permission. There currently is no way to expose the clipboard.readText API to web content since no permission system exists for it outside of extensions. This preserves the same use conditions as document.execCommand(“paste”).

In addition, the text versions of the API are the only ones available in Firefox 63. Support for the more general clipboard.read() and clipboard.write() API are awaiting clarity around the W3C spec and will be added in a future release.

Selecting Multiple Tabs

One of the big changes coming in Firefox 63 is the ability to select multiple tabs simultaneously by either Shift- or CTRL-clicking on tabs beyond the currently active tab. This allows you to easily highlight a set of tabs and move, reload, mute or close them, or drag them into another window. It is a very convenient feature that power users will appreciate.

In concert with this user-facing change, extensions are also gaining support for multi-select tabs in Firefox 63. Specifically:

The tabs.onHighlighted event now handles multiple selected tabs in Firefox.

The tabs.highlight API accepts an array of tab indices that should be selected.

The tabs.Tab object properly sets the value of the highlighted property.

The tabs.query API now accepts “highlighted” as a parameter and will return an array of the currently selected tabs.

The tabs.update API can alter the status of selected tabs by setting the highlighted property.

A huge amount of gratitude goes to Oriol Brufau, the volunteer contributor who implemented every single change listed above. Without his hard work, multi-select tabs would not be available in Firefox 63. Thank you, Oriol!

P.S. Oriol wasn’t satisfied doing all of the work for multi-select tabs, he also fixed several issues with extension icons.

What You’ve Been Searching For

Firefox 63 introduces a completely new API namespace that allows extensions to enumerate and access the search engines built into Firefox. Short summary:

The new search.get() API returns an array of search engine objects representing all of the search engines currently installed in Firefox.

Each search engine object contains: name (string) isDefault (boolean) alias (string) favIconUrl (URL string)

The new search.search() API takes a query string and returns the results. It accepts an optional search engine name (default search engine is used, if omitted) and an optional tab ID where the results should be displayed (opens a new tab, if omitted).

Extensions must declare the search permission to use either API.

The search.search() API can only be called from inside a user-input handler, such as a button, context menu or keyboard shortcut.

More Things to Theme

Once again, the WebExtensions API for themes has received some significant enhancements.

Finally, there is a completely new feature for themes called theme_experiment that allows theme authors to declare their own theme properties based on any Firefox CSS element. You can declare additional properties in general, additional elements that can be assigned a color, or additional elements that can be images. Any of the items declared in the theme_experiment section of the manifest can be used inside the theme declaration in the same manifest file, as if those items were a native part of the WebExtensions theme API.

theme_experiment is available only in the Nightly and Developer editions of Firefox and requires that the ‘extensions.legacy.enabled’ preference be set to true. And while it also requires more detailed knowledge of Firefox, it essentially gives authors the power to completely theme nearly every aspect of the Firefox user interface. Keep on eye on MDN for detailed documentation on how to use it (here is the bugzilla ticket for those of you who can’t wait).

Similar to multi-select tabs, all of the theme features listed above were implemented by a single contributor, Tim Nguyen. Tim has been a long-time contributor to Mozilla and has really been a champion for themes from the beginning. Thank you, Tim!

Gaining More Context

We made a concerted effort to improve the context menu subsystem for extensions in Firefox 63, landing a series of patches to correct or enhance the behavior of this heavily used feature of the WebExtensions API.

Context menus will continue to be a focus and you can expect to see even more improvements in the Firefox 64 timeframe.

A Motley Mashup of Miscellany

In addition to the major feature areas mentioned above, a lot of other patches landed to improve different parts of the WebExtensions API. These include:

Thank You

A total of 111 features and improvements landed as part of Firefox 63, easily the biggest upgrade to the WebExtensions API since Firefox Quantum was released in November of 2017. Volunteer contributors were a huge part of this release and a tremendous thank you goes out to our community, including: Oriol Brufau, Tim Nguyen, ExE Boss, Ian Moody, Peter Simonyi, Tom Schuster, Arshad Kazmi, Tomislav Jovanovic and plaice.adam+persona. It is the combined efforts of Mozilla and our amazing community that make Firefox a truly unique product. If you are interested in contributing to the WebExtensions ecosystem, please take a look at our wiki.