How often does Spotlight [re-] index?

Hi, Graham.

Spotlight updates its indices on the fly. If a document is new, changed, or deleted, the indexes are updated nearly in real-time.

There are two approaches to rebuilding the Spotlight indices, i.e. reindexing your startup disk:

1. The GUI way: see "Spotlight: How to re-index files and folders."

2. The Terminal way:

2.1. In terminal, type the following command exactly as written:

sudo mdutil -E /

then press Return.

2.2. Type your Admin password when prompted, then press Return.

2.3. You'll receive a confirmation message that the index will be rebuilt automatically. Indexing will begin shortly thereafter.

I prefer the Terminal approach over the GUI (Privacy) approach as there are some anomalies assocaited with using Privacy. You can run into anomalies in Tiger if you combine Privacy with mdutil. For details, see my "Stop Spotlight Indexing" FAQ.

Good luck!

😉 Dr. Smoke
Author: Troubleshooting Mac® OS X

---
Note: The information provided in the link(s) above is freely available. However, because I own The X Lab™, a commercial Web site to which some of these links point, the Apple Discussions Terms of Use require I include the following disclosure statement with this post:

I may receive some form of compensation, financial or otherwise, from my recommendation or link.

Indexing is to save resources and time.

Some people like to locate a file based on some characteristic - indexing takes those limited characteristics and pre-searches each and every file once to determine all possible search values and stores that information in a file called an index.

Now whenever a single file changes - the system updates the index - so barring crashes or flaws in the design - the index is always up to date.

Now when you need to find something based on size or date or type or content - the computer only has to search an index rather than the entire hard drive.

For me - I have 300GB of data on my disk - but my index is 200MB - a 200 MB file can fit in RAM and be searched in milliseconds - the drive would take 3 to 4 hours to search. If I make ten searches in a day, it becomes apparent how cool and powerful an up to date index is.

As to why it misses things - someone decided that the missing items were not important (or the administrator of your computer have set up certain files to be ignored). You can choose what is important for spotlight to index as well as make your own filters if Apple hasn't chosen wisely for your needs.

I cannot understand WHY Spotlight indexes things (and misses many things in the process). What is the POINT of indexing?