Apple released its newest version of the Macintosh operating system, macOS 12 Monterey, on October 26th, 2021. Monterey is compatible with most Macs made in 2015 or later with a few notable exceptions: Early 2015 iMacs and 2015 MacBooks (not MacBook Pros) are not compatible. 2013 or later Mac Pros, and 2014 and later Mac Minis are also compatible with Monterey. Monterey is currently pre-installed on most newly purchased Macintoshes and is required on the 14-inch and 16-inch MacBook Pro systems announced in mid-October 2021.

At the time of release, Information Systems & Computing (ISC) suggested that all University users considering upgrading their devices to Monterey adopt a “wait and see” approach and continue to use earlier supported versions of macOS. This short wait allowed for initial bugs and compatibility issues with Monterey to be identified and either fixed or avoided.

As of today, November 15th, 2021, Monterey is now cleared for general use by Penn constituents. ISC recommends that those with niche needs of untested apps or features continue to exercise caution in updating their macOS devices. In particular, users of high-end audio, video, and 3D applications should verify compatibility with their application vendors before upgrading.

Compatibility at Penn

ISC and others across the University have tested macOS Monterey and has found that many commonly used products and software function as expected, including:

  • Adobe Acrobat Reader
  • Chrome .current
  • Code42
  • CrowdStrike
  • Fetch 5.8.2
  • Firefox .current
  • Firefox ESR
  • GlobalProtect VPN client
  • Microsoft Office 365
  • MobileConnect for Vonage Enterprise
  • PowerTerm
  • SecureW2 JoinNow
  • Symantec Endpoint Protection

One potential issue of note is a change in the manner that Safari 15 accesses SSL-protected websites. Safari 15 comes preloaded with an exhaustive list of web domains, including, that are SSL-enabled and will force an https connection to any of these domains. This behavior persists even when a user manually enters an http:// prefix into the URL. While overall a positive security enhancement, this can potentially cause issues with captive networks that utilize web redirects like AirPennNet-Guest and Connect to AirPennNet. Users logging on to these kinds of captive networks will need to enter a site Safari does not “know” about to reach their splash pages, as https traffic cannot be redirected.

A final note: as Penn rolls formal support for Monterey, it’s also time for an important reminder about older macOS versions. Given Apple’s usual support practice, the security patch released in July 2021 for macOS 10.14.x Mojave was likely the final one they will make available. Where possible, systems running macOS 10.14.x should be upgraded to macOS 10.15.x or later. Systems incapable of running macOS 10.15.x or later—now at least five years old and generally more than eight years old—should be considered for retirement.

My thanks go out to many testers across the University who assisted with this evaluation, including Dan Cipolla, JM Conway, Nate Cosgrove, Matt Frew, Ian Kelley, Walt Mankowski, and David Siedell.