eXtensions - Friday 20 October 2017


eXtensions - System Preferences in macOS High Sierra: Extensions

By Graham K. Rogers

Users & Groups

In macOS, High Sierra, some panels have seen changes in System Preferences, while some are unchanged. Extensions manages the way additional control files are used by the Mac, including those from 3rd-party developers. The use of this has expanded considerably in the last year or so and there are some changes with this update.

Extensions for Apple operating systems existed since long before OS X: indeed, the name of this site and the column I wrote for the Bangkok Post came from this and the new emphasis (then) on the X of OS X (OS Ten, not X). These files add functions to applications: extending their normal capabilities. Some other functions are also available via the Services menu for each application.

Stickies When demonstrated at the World Wide Developers Conference in June 2014, an image captured from Safari was added to an email and then Markup was used to add information and comments to the photograph. Markup was one of the first extensions available and works in apps that already mix text and images, such as TextEdit and Stickies.

It has now been added to Photos. Not all apps have such extensibility. As more developers (or Apple) increase the availability of extensions, functions will be added to those apps that are able to use such new features.

The single panel has two parts: to the left the types of extensions. These have been changed slightly and are now: All, Actions, Photos Editing, Share Menu, Today. Below each extension type, is a summary (in grey) of what is available. When one of the types is highlighted, any extensions installed are shown in the main panel to the right.


  • All - All third-party extensions. On the MacBook, this shows several Photos extensions, Twitter and others, each with a checkbox. Alongside each checkbox is the service (e.g. Finder, Photos) that the extension works with. Others installed in Share or Today may not be shown here.

  • Actions - I have only two extensions installed: Markup and Pixelmator's Repair Tool. A checkbox alongside each indicates that they are active. If the Markup checkbox is deselected, it is immediately unavailable in apps. When the box is checked again, it is available right away. Markup has a number of ways to make comments or annotations on an image used in an application that allows this, including the use of a signature.

  • Photos Editing - This was not in the original implementation of the Extensions preferences and its name has been changed (in Sierra it was Photos). It allows several third party developers to produce creative extensions that provide useful additions for the Photos app, expanding the value of that application significantly.

    [At the time of writing, a couple of the extensions are not working properly with HEIC/HEIF image files. If this happens the standalone version of the application can be used: an image may need to be exported from Photos, or accessed from the application's Open menu (in both cases the file is converted to a suitable format).]


  • Share Menu - this includes a list of several applications from which it is already possible to export or otherwise share data. These include Apple developed applications (including Mail, Messages and AirDrop) as well as a number of 3rd party ones, such as Facebook, Twitter and Flickr. Those that are currently in use, have their boxes checked. A number of other extensions that are installed, but are not used, are unchecked. These include certain Asian services, including Weibo and Tudou that I never access.

  • Today is the other half of the Notifications Center panel in which a user may display icons that access specific functions or display certain information. The Notifications half is controlled in System Preferences > Notifications.

    In my "Today" display I have Stocks, Weather, World Clock, and several other such data displays, including Social (allowing links to sites like Facebook and Twitter if wanted). Extensions that are installed, but not used, are unchecked.

The extensions here are installed for system-wide use, so those installed specifically for Safari (for example) are not shown here. It is expected that more extensions will appear, but will be part of new applications (or updates to already-installed applications).

As more information becomes available, or if changes are made, this page will be updated.

See Also:

Graham K. Rogers teaches at the Faculty of Engineering, Mahidol University in Thailand. He wrote in the Bangkok Post, Database supplement on IT subjects. For the last seven years of Database he wrote a column on Apple and Macs. After 3 years writing a column in the Life supplement, he is now no longer associated with the Bangkok Post. He can be followed on Twitter (@extensions_th)



Made on Mac

For further information, e-mail to

Back to eXtensions
Back to Home Page

All content copyright © G. K. Rogers 2017