After upgrading to Golden Gate, many people notice the same things: search results are incomplete, Siri AI can't find files it should know about, the fans come on at odd times, and the battery drains faster than it did on Tahoe. Almost always, the cause is Spotlight building its index.

What's different in macOS 27 is how much work that index involves, how little the system tells you about its progress, and how easily that work gets paused. Understanding the mechanics turns "why is this taking forever" into something you can actually speed up.

What's being built

Earlier versions of Spotlight mostly catalogued file names, metadata, and text content. Golden Gate goes further. Spotlight and Siri AI are now integrated, and search is semantic: you can ask a question in natural language and get an answer instead of a list of filenames.

That requires a different kind of index. Instead of a flat catalogue, macOS converts your files and their contents into vectors, numerical representations that capture meaning. Generating those embeddings for years of documents, email, messages, and photos is far heavier work than traditional indexing.

Apple began this rebuild with macOS 26.6. If you installed that update and left your Mac running, part of the work may already be done. If you skipped it or upgraded straight from Sequoia, it starts from zero.

Mail also rebuilds its own search index after the upgrade, and Photos re-analyzes your library. All three compete for the same resources.

Why it's slow on purpose

On a Mac, indexing doesn't run flat out. Spotlight's knowledge service submits its heavy jobs to macOS's background task scheduler, which runs them in short bursts only when the Mac meets conditions for power, temperature, available resources, and inactivity.

The inactivity part is what catches people out:

  • Any keyboard, mouse, or trackpad input marks the Mac as active. After you stop, the system waits about three minutes before treating the Mac as idle again.
  • Media playback keeps the Mac active. A paused YouTube tab or a music app can hold off indexing for hours.
  • Battery and heat pause it. On battery, or when the Mac is warm, the scheduler defers the work.

So a MacBook used all day on battery, then closed at night while unplugged, may make almost no progress for days. That's not a bug. The system is protecting your battery and responsiveness, at the cost of taking longer.

There's another reason progress looks stuck: Spotlight can ask apps to resubmit some or all of their searchable content, so an indexing percentage can barely move even after a long session. And the embedding work is tracked separately from basic indexing.

How to tell whether it's running

Golden Gate doesn't show a persistent indicator in System Settings, unlike iOS, which displays a notice while Search and Siri are optimizing.

Check Spotlight itself. Press Command-Space. While indexing is in progress, Apple says you may see an indexing indicator at the top of the Spotlight or Siri window.

Check Activity Monitor. Open it and sort by CPU. Processes like mds_stores, mdworker_shared, and spotlightknowledged near the top mean indexing is active. photoanalysisd and mediaanalysisd mean Photos is doing its own analysis.

Check that indexing is enabled for your drive:

mdutil -s /

Watch the knowledge service in real time:

log stream --predicate 'process == "spotlightknowledged"' --style compact

Lines scrolling by mean it's working. Press Control-C to stop. You won't get a percentage, but you'll see whether it's running or waiting.

See what's keeping the Mac "active":

pmset -g assertions

Look for UserIsActive and media-related assertions. If a browser or media app is holding one while you're away, that's what's blocking indexing.

How to help it finish

  1. Plug in. Indexing completes faster on power. This is the single biggest factor.
  2. Leave the Mac alone overnight, awake. Close media apps and browser tabs that play audio or video. For a MacBook, keep the lid open or use a display, and in System Settings > Battery > Options, turn on preventing automatic sleeping on power adapter when the display is off. Turn it off again when indexing is done.
  3. Stay online. Apple notes indexing goes faster on Wi-Fi or Ethernet, because Mail and other data may need to download to be indexed.
  4. Keep it cool. Don't leave a MacBook on a bed or in a closed bag while indexing.
  5. Don't kill the processes. Force-quitting indexing processes doesn't save the work; it restarts later.
  6. Give it several nights. On a Mac with a large Photos library and years of mail, three or four nights plugged in is normal.

Excluding folders you don't need searched

If you have folders full of data you'll never search, like virtual machine images, build folders, large archives, or media caches, you can exclude them to reduce the load.

Go to System Settings > Spotlight and open Search Privacy. Add the folders to the list of locations Spotlight won't index.

Don't exclude your home folder or Documents. Siri AI relies on the index to answer questions about your own files.

When to rebuild the index

Only rebuild if indexing is clearly broken, not just slow: for example, searches still miss files a week after upgrading while the Mac has had several nights plugged in, or indexing processes run constantly for days with no sign of settling.

Apple's method is to add your startup disk to Spotlight's Search Privacy list, wait a few seconds, then remove it. That triggers a full reindex. In Terminal, the equivalent is: 

sudo mdutil -E /

Understand the cost: this erases the index and starts the whole process over, including the heavy embedding work. Do it once, plug in overnight, and don't repeat it.

The short version

  • Golden Gate builds a new semantic index for Spotlight and Siri AI. It's much heavier than traditional indexing.
  • It runs only in short bursts while the Mac is idle, cool, and ideally on power. Input and media playback pause it.
  • There's no progress bar in System Settings. Use Activity Monitor, log stream, and pmset -g assertions to see what's happening.
  • Plug in, stay online, close media apps, and leave the Mac awake overnight for a few nights.
  • Rebuild the index only if it's truly stuck, and only once.