Spotlight index
Also known as: Spotlight indexing, rebuild Spotlight index, mds Mac
The Spotlight index is the searchable database macOS builds of your files, apps, and their contents so search returns instant results. It uses some disk space and can be rebuilt, which temporarily raises CPU and disk activity.
- A searchable database of files and their contents
- An index of pointers, not copies of your data
- Can be excluded or rebuilt via Spotlight Privacy settings
What Spotlight indexes
macOS continuously scans your drives and records file names, metadata, and text content in a hidden index so Spotlight (Command-Space) and Finder search can answer instantly. The index is a cache of pointers, not copies of your files, so its footprint is modest compared with the data it covers.
After a macOS update, a new drive, or a large file import, you may notice the Mac running warm while Spotlight re-indexes. This is normal and settles once indexing finishes.
Excluding folders or rebuilding
To stop indexing certain locations, add them under System Settings > Spotlight > Search Privacy (older macOS: System Preferences > Spotlight > Privacy). Removing a folder later lets it be re-indexed. A corrupt index that causes missing or stale search results can be rebuilt by adding then removing a drive from that Privacy list, which forces macOS to index it fresh.