macOS High Sierra, designated as version 10.13, represents a pivotal moment in the evolution of Apple’s desktop operating system. Released on September 25, 2017, it followed the tradition established by OS X Mountain Lion and OS X El Capitan—serving as a refinement-focused "tock" year in Apple’s development cycle. While it did not introduce a radical visual overhaul, its internal architectural changes laid the groundwork for the modern macOS experience seen today. As of November 12, 2020, macOS High Sierra reached its end-of-life status and no longer receives security patches or software updates from Apple.

The Current Status and Security Profile of macOS 10.13

Using macOS High Sierra in a modern computing environment carries inherent risks that users must acknowledge. Because the operating system is classified as obsolete, it lacks protection against modern cybersecurity threats. Vulnerabilities discovered in the years following 2020 remain unpatched, making devices running this version susceptible to malware, ransomware, and exploit kits that target known flaws in the kernel or the Safari browser.

Beyond direct security risks, software isolation is a significant factor. Major software developers, including Adobe, Microsoft, and even Google, have ceased support for High Sierra. This means the latest versions of creative suites, productivity tools, and web browsers cannot be installed. Users are often forced to use legacy versions of software, which may lack modern features and further increase the security surface area due to their own unpatched vulnerabilities.

Core Architectural Innovations

Despite its age, macOS High Sierra introduced three fundamental technologies that fundamentally changed how Mac hardware interacts with data and graphics.

Apple File System (APFS)

The most significant change in High Sierra was the introduction of the Apple File System (APFS) as the default for Macs with all-flash storage. Replacing the aging HFS+ (Hierarchical File System Plus), which had served Apple for decades, APFS was engineered specifically for solid-state drives (SSDs).

Technicians and power users noted an immediate improvement in file operation speeds. APFS utilizes a 64-bit architecture, supporting over 9 quintillion files on a single volume. Key features include:

  • Cloning: This allows the system to create nearly instantaneous copies of files without consuming extra storage space. Instead of duplicating data, the file system points to the same data blocks until a change is made.
  • Snapshots: APFS enables the creation of a read-only instance of the file system at a specific point in time, facilitating much faster backups and system recovery through Time Machine.
  • Space Sharing: Multiple volumes can share the same pool of free space on a physical drive, eliminating the need for rigid partitioning.
  • Native Encryption: Unlike HFS+, which added encryption as an afterthought through FileVault 2, APFS was built with multi-key encryption support from the ground up.

Metal 2 Graphics API

High Sierra integrated Metal 2, the next generation of Apple's low-level graphics API. This update was crucial for developers aiming to extract maximum performance from the GPU. Metal 2 introduced support for external graphics processors (eGPUs) via Thunderbolt 3, allowing older or less powerful Macs to utilize desktop-class graphics cards for rendering, gaming, and machine learning.

Furthermore, Metal 2 provided the foundation for Virtual Reality (VR) content creation on the Mac. For the first time, developers could use tools like SteamVR and the HTC Vive headset natively within the macOS environment, provided the hardware met the steep graphical requirements.

High Efficiency Video Coding (HEVC)

With the rise of 4K and 8K video, storage efficiency became a priority. High Sierra added native support for High Efficiency Video Coding (HEVC), also known as H.265. This standard allows for video compression that is up to 40% more efficient than the previous H.264 standard while maintaining the same visual quality. For users working with high-resolution media, this meant faster streaming and smaller file sizes for local storage. Alongside HEVC, Apple introduced HEIF (High Efficiency Image File Format) to optimize the storage of photos captured on iPhones running iOS 11 and later.

Application Improvements and Refinements

While the core of High Sierra was about technical stability, several native applications received significant functional updates.

Safari 11: Privacy and Performance

Safari 11 introduced Intelligent Tracking Prevention (ITP). This feature uses machine learning to identify and block the data used by advertisers to track user behavior across different websites. It was a major step forward in user privacy. Additionally, Safari 11 gave users the power to disable autoplay videos on a per-site basis and allowed for custom settings for Reader view and page zoom.

Photos: Advanced Editing Tools

The Photos app in High Sierra moved closer to professional-grade software. It introduced a persistent sidebar for better organization and advanced editing tools such as Curves (for fine-tuning color and contrast) and Selective Color. The app also improved its integration with third-party editing extensions, allowing users to open a photo in an app like Photoshop, save changes, and have those changes reflected directly in the Photos library.

Mail and Notes

The Mail app received a storage optimization that reduced the disk space required for stored messages by approximately 35%. It also introduced "Top Hits" in search, which uses a user’s previous interactions to predict which emails are most relevant. In the Notes app, Apple added the ability to create simple tables and pin important notes to the top of the list for quick access.

Hardware Compatibility and System Requirements

To run macOS High Sierra, a Mac must meet specific hardware criteria. Generally, any Mac capable of running macOS Sierra (10.12) is compatible with High Sierra.

Supported Mac Models

  • iMac: Late 2009 or newer
  • iMac Pro: 2017 models
  • MacBook: Late 2009 or newer
  • MacBook Pro: Mid 2010 or newer
  • MacBook Air: Late 2010 or newer
  • Mac Mini: Mid 2010 or newer
  • Mac Pro: Mid 2010 or newer

Minimum Technical Specifications

  • Memory (RAM): A minimum of 2 GB is required, though 4 GB or 8 GB is highly recommended for stable performance.
  • Storage: At least 14.3 GB of available storage is needed to perform the initial upgrade.
  • Operating System: The device must be running at least OS X Mountain Lion 10.8 to upgrade directly through the Mac App Store.

It is important to note that while these models support the OS, specific features like HEVC hardware acceleration require a Mac with a 6th-generation Intel processor (Skylake) or newer. Similarly, the transition to APFS is only automatic for Macs equipped with internal SSDs; those with traditional Hard Disk Drives (HDDs) or Fusion Drives may remain on HFS+ unless manually converted (though this was officially discouraged in earlier versions of 10.13 for Fusion Drives).

Preparing for Installation and Upgrading

For users managing legacy hardware that requires High Sierra for specific software compatibility, the installation process should be approached with caution.

Step 1: Data Backup

Before any system upgrade, a full backup via Time Machine or a bootable clone (using tools like Carbon Copy Cloner) is essential. If the conversion to APFS fails during installation, data loss can occur.

Step 2: Compatibility Check

Ensure that all mission-critical 32-bit applications are ready for the transition. High Sierra was the final version of macOS to support 32-bit apps without significant performance warnings, but it did begin the transition by alerting users that 32-bit apps would eventually become incompatible with future versions of macOS (starting with Catalina).

Step 3: Downloading the Installer

Since High Sierra is no longer the current OS, it is not prominently displayed in the App Store search. Users must often navigate through the "Purchased" tab or use direct links provided by Apple Support to access the installer.

Challenges of Using High Sierra in 2024 and 2025

Operating a Mac on version 10.13 today presents several practical hurdles.

Web Browser Limitations

The version of Safari included with High Sierra (Safari 13.1.2) cannot load many modern websites due to outdated security protocols (TLS 1.3 requirements). While some third-party browsers like Firefox or Chrome previously offered support, they have since moved their minimum requirements to macOS 10.15 Catalina or higher. Users may find success with "legacy" browser projects specifically maintained for older macOS versions, though these are community-led and carry their own risks.

The 32-Bit Bridge

High Sierra is often kept on older machines specifically to run legacy 32-bit software that is incompatible with macOS Catalina and beyond. This includes older versions of Adobe Creative Suite (CS6) or specialized industrial software. For these users, the machine should ideally be kept offline or behind a robust hardware firewall to mitigate security risks.

Certificate Issues

In recent years, many "root certificates" that macOS High Sierra relies on to verify the identity of websites have expired. This often results in "Your connection is not private" errors in browsers. While it is possible to manually update these certificates via the Keychain Access utility, it is a complex task that requires technical expertise.

Frequently Asked Questions

Can I upgrade from macOS High Sierra to macOS Sonoma?

Not directly. Hardware that officially supports High Sierra is generally too old to support macOS Sonoma. However, some users utilize third-party "patchers" to install newer macOS versions on unsupported hardware. This is not recommended for production environments as it can lead to system instability and driver issues.

Is macOS High Sierra still safe for online banking?

No. Due to the lack of security updates and the inability to run the most recent, secure versions of web browsers, using High Sierra for sensitive financial transactions is highly discouraged.

Why did my Mac not convert to APFS during the High Sierra install?

If your Mac has a traditional mechanical Hard Disk Drive (HDD) or an early Fusion Drive, the High Sierra installer typically skips the APFS conversion to avoid performance degradation. APFS is optimized for the seek times of flash storage; on mechanical drives, it can lead to increased fragmentation.

Does High Sierra support Dark Mode?

High Sierra features a "Dark Menu Bar and Dock" option in System Preferences, but it does not have the full-system Dark Mode that was introduced in its successor, macOS Mojave (10.14).

Summary of macOS High Sierra

macOS High Sierra remains a significant version in the history of the Mac for its introduction of the Apple File System and Metal 2. It serves as the ultimate destination for many iconic Mac models from the 2010-2011 era. While it provided essential refinements and performance boosts at the time of its release, its current status as an unsupported operating system makes it a liability for general-purpose computing. For users who must remain on 10.13 for legacy software support, extreme caution and limited network exposure are the best strategies for maintaining a stable and secure environment.