Quick Summary
Error 101 on macOS typically indicates a problem with Spotlight, macOS's indexing service. More specifically, it often suggests that the Spotlight index has become corrupted or incomplete, preventing accurate search results.
Common Causes
- Corrupted Index Files: The index files maintained by Spotlight can become corrupted due to various factors, such as system crashes, disk errors, or incomplete updates.
- Insufficient Disk Space: If the drive containing the Spotlight index runs low on storage space, Spotlight may not be able to properly update or maintain the index, leading to errors.
- Software Conflicts: Conflicting software, especially third-party search or indexing tools, can interfere with Spotlight's operation and cause indexing issues.
- File System Errors: Underlying file system errors on the disk can prevent Spotlight from correctly accessing and indexing files.
Step-by-Step Fixes
Method 1: Rebuild the Spotlight Index Using System Preferences
Step 1: Open System Preferences from the Apple menu.
Step 2: Click on 'Spotlight'.
Step 3: Select the 'Privacy' tab.
Step 4: Drag the icon of your entire hard drive (usually named 'Macintosh HD') to the list of locations that Spotlight is prevented from searching. If you do not see your hard drive icon on the desktop, you can find it in Finder's sidebar under 'Locations'.
Step 5: Alternatively, you can click the '+' button and manually add your hard drive.
Step 6: Wait a few seconds, then select your hard drive from the list and click the '-' button to remove it. This forces Spotlight to re-index your drive.
Step 7: Spotlight will begin re-indexing. This may take several hours, or even overnight, depending on the size of your drive and the number of files.
Method 2: Rebuild the Spotlight Index Using the Terminal
Step 1: Open Terminal from the /Applications/Utilities/ folder.
Step 2: Type the following command and press Enter: sudo mdutil -E /
Step 3: You'll be prompted for your administrator password. Enter it and press Enter. Note that the password will not be displayed as you type.
Step 4: The command will erase the existing Spotlight index for the root volume (your main hard drive) and start re-indexing.
Step 5: Re-indexing can take several hours or even overnight. You can monitor the progress by typing sudo mdutil -s / in the Terminal.
Method 3: Check Disk for Errors
Step 1: Open Disk Utility (located in /Applications/Utilities/).
Step 2: Select your startup disk in the sidebar.
Step 3: Click the 'First Aid' button.
Step 4: Click 'Run' to start the disk repair process. Disk Utility will check for and attempt to repair any errors it finds on the disk.
Step 5: Follow any on-screen prompts. If Disk Utility finds errors it cannot repair, you may need to back up your data and reformat the drive or seek professional help.
Method 4: Disable and Re-enable Spotlight
Step 1: Open Terminal from the /Applications/Utilities/ folder.
Step 2: To disable Spotlight, type the following command and press Enter: sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist
Step 3: You'll be prompted for your administrator password. Enter it and press Enter.
Step 4: Wait a few minutes.
Step 5: To re-enable Spotlight, type the following command and press Enter: sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist
Step 6: Spotlight should begin re-indexing automatically.