You're sitting there looking at macOS 10.12 Sierra. It feels fine, right? But the web is moving on. Apps are starting to demand a newer version of Metal, and security patches for Sierra are basically a relic of the past. If you want to upgrade to High Sierra from Sierra, you aren't just changing a version number; you are fundamentally changing how your Mac talks to its own hard drive.
It's a big deal.
Honestly, the jump to 10.13 was one of the most technical shifts Apple ever pulled off under the hood. While the interface looks nearly identical to its predecessor, the file system swap from HFS+ to APFS is a "point of no return" moment for many users. If you have an SSD, your Mac is about to get way faster. If you're on an old spinning hard drive, things get... complicated.
Why the High Sierra jump is actually a massive deal
When Apple released High Sierra back in 2017, they didn't focus on flashy features. They focused on "plumbing." This is the version that introduced HEVC (H.265) video support and the initial stages of external GPU (eGPU) compatibility. But the crown jewel—and the thing that causes the most anxiety during an upgrade—is the Apple File System (APFS).
Old-school Sierra uses HFS+, a file system architecture that's decades old. It was built for floppy disks and spinning platters. APFS is built for flash storage. It makes copying files instantaneous and prevents crashes from corrupting your entire directory.
Does your Mac even want this?
Before you go hitting "Update," you need to know if your hardware is invited to the party. Generally, if you're running Sierra, you can run High Sierra. Apple kept the hardware requirements the same for both versions. We're talking MacBook and iMac models from late 2009 or later, and MacBook Air, Pro, Mac mini, and Mac Pro models from 2010 or later.
But here is the catch: just because you can doesn't mean you should without a plan.
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If you're rocking an older Mac Pro with a non-Metal compatible graphics card, you're going to see a black screen. High Sierra requires Metal-capable GPUs to render the UI properly. Most users with standard MacBooks won't have this issue, but for the "cheese grater" Mac Pro enthusiasts, this is a major hurdle.
The Preparation Phase: Don't skip this or you'll regret it
Backup. Just do it.
Seriously, I’ve seen enough "flashing folder with a question mark" icons to last a lifetime. Because the upgrade to High Sierra from Sierra involves a literal conversion of your file system, any power flicker or disk error during the process can turn your data into digital confetti.
Use Time Machine. Or better yet, use Carbon Copy Cloner to make a bootable clone. If the High Sierra installer decides it doesn't like your partition map, you'll want a way to get back to Sierra in ten minutes, not ten hours.
Check your disk health too. Open Disk Utility, select your internal drive, and click First Aid. If it shows "overlapping extent allocations" or other cryptic errors, fix them now. High Sierra's installer is much pickier than Sierra's. It will fail if it detects even a hint of directory corruption.
The APFS Factor
If your Mac has an SSD, the installer will automatically convert your drive to APFS. You cannot opt out of this in the later versions of the installer.
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For those using a standard mechanical Hard Disk Drive (HDD) or a Fusion Drive, Apple's stance shifted over time. Initially, Fusion Drives didn't get APFS, then they did, then they didn't. In the final stable build of 10.13.6, mechanical drives usually stay on HFS+ for performance reasons. APFS on a spinning disk is painfully slow because of how it handles metadata seeking.
Step-by-Step: The actual upgrade path
Since we're in 2026, finding the installer isn't as simple as opening the "Updates" tab in the App Store. Apple hides old versions.
- Find the Link: You usually have to go through a specific Apple Support KB article to find the hidden Mac App Store link for High Sierra.
- The Download: It’s about a 5GB file. Once it downloads, it will likely try to open automatically.
- The Firmware Update: This is the part that scares people. Your screen might go black for a long time. You might hear a long, loud beep. Do not touch the power button. High Sierra often includes a firmware update to allow your Mac to recognize APFS volumes at the BIOS/EFI level.
- The Installation: This usually takes 30 to 45 minutes. If the progress bar looks stuck at "1 minute remaining" for half an hour, just wait. It’s likely performing the HFS+ to APFS conversion.
What about your apps?
Sierra was the last version where some 32-bit apps felt truly "at home." High Sierra starts the aggressive push toward 64-bit. You'll get warnings. You might find that old version of Adobe Creative Suite 6 starts acting a bit twitchy.
If you rely on Microsoft Office 2011, be warned: it is officially "unsupported" on High Sierra. It might work, or it might crash every time you try to save a Word doc. If your livelihood depends on a specific piece of software, check the compatibility on RoaringApps before you pull the trigger.
Common Roadblocks and how to smash them
"The installer resources were not found."
This error is a classic. It usually happens because the system clock on your Mac is out of sync or the certificate for the installer has expired. If you see this, you might need to go into Terminal and manually set the date back to 2018 or 2019 just to get the installer to run.
Another common headache is the "File system verify or repair failed" error. If this happens, your only real choice is to wipe the drive and perform a clean install. This is why we backed up earlier.
Is it actually faster?
Yes and no.
On an SSD, the upgrade to High Sierra from Sierra feels like a breath of fresh air. Files move faster. The system boots slightly quicker. But on an older iMac with a 5400-RPM hard drive? It can feel sluggish. High Sierra does more background indexing, and the new window management features demand more from the GPU.
Expert Insights: Why you might want to stop at High Sierra
High Sierra is often considered the "end of the road" for many classic Macs. It’s the last version that supports many older graphics cards and the last version before Apple removed support for 32-bit apps entirely in Mojave and Catalina.
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If you have a library of older games or professional plugins that haven't been updated since 2015, High Sierra is your safe haven. It's the bridge between the old world of Mac OS X and the new world of macOS.
Actionable Next Steps
If you're ready to make the jump, here is your checklist.
- Verify your GPU: If you're on a Mac Pro, ensure you have a Metal-compatible card (like an AMD Radeon RX 580).
- Clear 15GB of space: The installer needs room to breathe during the conversion process.
- Check your FileVault status: Sometimes it's smoother to decrypt your drive before the upgrade and re-encrypt it after the APFS conversion is done.
- Download the installer: Use the official Apple Support links to ensure you aren't getting a tampered version from a third-party site.
- Run Disk Utility: Fix any errors on your Sierra install before you even think about hitting "Continue."
Once you’re on High Sierra, make sure to run all the security updates. Even though it's an older OS, the final "Security Update 2020-006" fixed a lot of late-stage vulnerabilities. You'll have a more stable, more secure, and more "modern" feeling machine without having to buy a new M3 MacBook.