What is mdsync on Mac?

Mdsync is a background service that manages Spotlight indexing on macOS, enabling you to search for any file or application on your Mac. It ensures that Spotlight remains current.

Spotlight is one of the fastest and most efficient methods for finding nearly anything on your Mac. It's a built-in search tool that's highly effective and dependable, and many Mac power users find it indispensable. However, it's only due to the mdsync service that Spotlight performs so well.

Mdsync on Mac ensures that Spotlight stays updated, so that when you create and save new files to your system, they'll appear in your Spotlight search results when you need to find them later.

Why does mdsync consume so much CPU on Mac?

It's not unusual to encounter high CPU usage from mdsync on Mac, similar to other system functions like the CCXProcess. Here are some of the most common reasons why mdsync uses a significant amount of CPU resources:

• Re-indexing after a Mac OS update
• Large files being created or modified
• Issues with external drives
• Ongoing Time Machine backups

If you're unsure whether mdsync is causing your Mac to slow down, you can check the Mac's performance in Activity Monitor and see which processes are consuming the most power. Simply open Activity Monitor from the Applications > Utilities folder, then look at the CPU% column for each process.

When to leave mdsync alone

It's always best to avoid disrupting mdsync if possible, since stopping the task on Mac prevents Spotlight from updating, making it less accurate. However, there are times when it's especially important to let mdsync complete its indexing.

For instance, you shouldn't interrupt mdsync after setting up macOS for the first time, after installing a new software update, during a Time Machine backup, or after connecting a new drive containing a large amount of data. Disabling it during these times will make Spotlight less effective.

We should be aware that occasional spikes in CPU usage from mdsync are entirely normal. If you allow the process to proceed, you'll usually find it stabilizes after a while. High CPU usage isn't a cause for concern unless it persists for an extended period.

How to resolve high CPU usage caused by mdsync

Although we recommend avoiding interference with mdsync, there may be instances when you have no choice, such as when it gets stuck. Here's how to address it:

1. Restart Mac in Safe Mode.
2. Disable Spotlight indexing.
3. Stop Spotlight indexing large folders.
4. Temporarily terminate mdsync via Terminal.

1. Restart Mac in Safe Mode

Booting your Mac into Safe Mode prevents certain software from loading and checks your startup disk to ensure there are no issues that could interfere with mdsync.

On an Apple Silicon Mac:

1. Shut down your Mac.
2. Press and hold the power button until you see Loading startup options.
3. Select a volume, press and hold the Shift key, then click Continue in Safe Mode.

On an Intel Mac:

1. Restart your Mac, then immediately press and hold the Shift key until you see the login window.
2. Log in to your Mac.

In Safe Mode, allow your computer to run for a while to give mdsync a chance to finish indexing. Use Activity Monitor, which is the task manager in Mac, to monitor its status, then Restart when it’s done.

2. Disable Spotlight indexing

If you never use Spotlight, you can disable indexing to stop mdsync from running. Here's how:

1. Open Terminal from Applications > Utilities.
2. Type sudo mdutil -a -i off and then hit Enter.

To turn Spotlight indexing back on later, simply repeat the steps above, but instead enter sudo mdutil -a -i on into Terminal.

3. Stop Spotlight indexing large folders

Rather than disabling Spotlight indexing altogether, you can keep it running but instruct it to ignore large folders that tend to slow things down. Do this:

1. Open System Settings and select Spotlight > Search Privacy.
2. Add large folders you don't want Spotlight to index by clicking the button, then click Done.

4. Temporarily terminate mdsync via Terminal

You can temporarily stop mdsync using Terminal when you think it's stuck and not functioning properly. Disabling and then re-enabling it often fixes unusual indexing issues. Follow these steps:

1. Open Terminal.
2. Type sudo mdutil -a -i off and then hit Enter to disable mdsync.
3. Wait a few seconds for the process to stop completely.
4. Type sudo mdutil -a -i on and then hit Enter to re-enable mdsync.

Conclusion

The mdsync process built into macOS can occasionally consume a lot of CPU power, potentially slowing down your Mac. While this is normal behavior from time to time, you may need to stop mdsync or restart Spotlight indexing using the solutions above if the process becomes stuck with high CPU usage.

We also suggest users clear their Mac's memory when their computer becomes sluggish. With MacKeeper’s Memory Cleaner, you can quickly and safely remove old data from your Mac’s RAM to make it faster and more stable.

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