Mdsync on Mac

What is mdsync on Mac?

Mdsync is a background process that handles Spotlight indexing in macOS, allowing you to search for any file or app on your Mac. It helps ensure Spotlight is always up-to-date.

Spotlight is one of the quickest and most effective ways to find almost anything on your Mac. It’s a built-in search tool that’s incredibly powerful and reliable, and we’ve found that Mac power users can’t live without it. But it’s only because of the mdsync process that Spotlight is so good.

Mdsync on Mac helps ensure Spotlight is always up to date, so that when you create and save new files to your system, they’ll appear in your Spotlight search results when you want to find them later.

Why does mdsync use so much CPU on Mac?

It’s not uncommon to find mdsync high CPU usage on Mac, as we’ve seen with other system functions like the CCXProcess. Here are some of the most common reasons why mdsync eats up CPU resources:

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

If you’re not sure whether mdsync is the reason why your Mac is suddenly running slowly, you can check Mac speed in Activity Monitor and see which processes are calling for the most power. Simply open Activity Monitor from the Applications > Utilities folder, then check the CPU% column for each process.

A note from our experts: 

 

When your Mac starts to feel sluggish, it could be low on memory or RAM—likely because old app data hasn’t been cleared properly. You can quickly and safely delete old data from your Mac’s RAM yourself in just a couple of clicks using MacKeeper’s Memory Cleaner.

 

Try this:

1. Download MacKeeper and install it.
2. Select the Memory Cleaner in the MacKeeper sidebar, then click Open.
3. Click Clean Memory to purge old data from RAM and speed up your Mac.

When to leave mdsync alone

It’s always best to avoid interfering with mdsync if you can, since when you end the task on Mac, it prevents Spotlight from updating and therefore makes it less accurate. But there are times when it’s particularly important to leave mdsync alone to finish indexing.

For example, you shouldn’t interrupt mdsync after setting up macOS for the first time, after installing a new software update, when performing a Time Machine backup, and after connecting a new drive that includes a large amount of data. Disabling it during this time will make Spotlight less effective.

We should be mindful of the fact that occasional spikes in CPU usage from mdsync are perfectly normal. If you allow the process to do its thing, you’ll usually find it settles down after a while. High CPU usage isn’t a cause for concern, unless it continues for an extended period of time.

How to fix high CPU usage caused by mdsync

Although we recommend not stopping the mdsync process, there may be times when you have no choice, like when it becomes stuck. Here’s how to fix it:

1. Reboot Mac into Safe Mode.
2. Disable Spotlight indexing.
3. Stop Spotlight indexing large folders.
4. Terminate mdsync temporarily via Terminal.

1. Reboot Mac into Safe Mode

Booting your Mac into Safe Mode prevents some 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. We’ll show you how:

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

Want 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

We don’t necessarily have to disable Spotlight indexing to make it more efficient. Instead, you can keep it running, but tell 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. Terminate mdsync temporarily via Terminal

You can temporarily terminate mdsync using Terminal when you feel like it’s stuck and not working correctly. Disabling and then re-enabling it again often fixes odd 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 sometimes eat up a lot of CPU power, which may slow down your Mac. While this is perfectly normal behavior from time to time, you may have to stop mdsync or restart Spotlight indexing using the solutions above if the process becomes stuck with high CPU usage.

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