I found this great information on Reddit:
How iOS 27 Indexing Works (What Redditors Report)
What It Is & Why It Runs
• Purpose: Rebuilds device search/index so Spotlight, Mail, Photos, and Siri yield better results. "it supposedly organizes your files so you can search for them quickly"
• Scope: The index in iOS 27 is much larger and more detailed than before, so initial creation can take far longer. "the index is being completely rebuilt... the index is therefore an order of magnitude larger, more specific, and hopefully also more informative"
Typical Duration & Variability
• Expected time: Multiple days is common; many users report >24–36 hours. "24 hours and my Iphone 17 hasn’t finished indexing."
• Not strictly tied to data size: Some devices with little or no data still index for days. "I have 0 and it’s indexing 24 hours now. I guess it always takes 2-3 days."
• Depends on device and buginess: Experiences vary—some finish <24h, others take several days or may be affected by beta bugs. "Mine was done in less than 24 hours on 16PM... noticing some minor bugs and heat issues"
Symptoms During Indexing
• Battery / heat / performance effects: Users often see temporary battery drain, heating, or lag while indexing. "Knowing the most powerful iPhone is still indexing gives me some sort of peace lol. My SE 3 has been stuck as well."
• UI visibility: iOS now shows an indexing indicator in Settings so you can tell when it's happening. "I like that it tells you this instead of the guessing game"
• Search/Siri partially limited until done: Search and Siri results can be incomplete while indexing runs. "When I searched for apps by names yesterday nothing was coming up. Today it’s partially working."
Causes, Workarounds & Troubleshooting
• Not location-specific: Indexing appears unrelated to being overseas. "It's nothing to do with location."
• Be patient / wait: Multiple commenters advise waiting; it's expected behavior after big updates. "Why not just wait? It will take a long time... it is reindexing your whole life on the device"
• Possible bug or beta instability: Some believe slow indexing may be a bug in the developer beta. "It might be a bug too. My indexing is taking quite some time..."
• Restores may help but are heavy-handed: A full restore might fix stuck indexing for some, but it’s not universally recommended. "A restore of the device would probably fix it"
Community Observations & Contrasts
• Historical precedent: Major iOS updates have long rebuilt indexes and caused temporary complaints about battery/heat. "Literally every major update does this. It's why newbs complain about bad battery performance / excessive heat"
• Mixed outcomes after completion: Some see improved performance and search quality after indexing finishes; others still notice minor bugs. "I think the delay is probably a bug at this point... I've asked Siri obscure questions... she's spot on 9/10"
• Siri access is separate: Getting access to the new Siri AI can be on a separate waitlist and is not strictly tied to indexing completing. "Indexing has nothing to do with Siri. My phone is still indexing. It’s a 17 pro but I’ve had the Siri since I updated the beta"
