Battery is noticeably worse since the update — how do you tell the real thing from the usual first-week explanation?

The reindexing explanation is real, it is overused, and there is a way to tell.

What actually happens after a major update. The device re-analyses a lot of content — rebuilding the search index, re-running photo analysis, and re-optimising app binaries. On a phone with a large photo library this is genuinely hours of work, and it is deliberately scheduled for when the phone is charging and idle, so it stretches over several nights rather than finishing in one go.

Why it gets overused as an excuse. Because it is unfalsifiable if you do not look. It becomes the answer to every complaint, including the ones where something is really wrong.

How to tell. Look at the battery breakdown by activity. What you want to know is whether the drain is on-screen or in the background:

• Background-heavy drain that shrinks each day is the settling-in story, and it is true.
• A single app at the top that you barely used is a real problem and it will not settle. This is the common case people mistake for reindexing.
• Screen-on drain being higher than before is not reindexing at all — that is a display or brightness change, and reindexing does not run while you are using the phone.

So look at whether one app is responsible before you accept the general explanation.

The boring answer, offered because it is right more often than any of the clever ones: give it a week of normal use, including a few nights on charge, before concluding anything.

Most of the settling work needs the phone plugged in and idle. If you have had three short nights since updating, the background work has barely run and you are measuring a phone mid-task.

A reasonable timeline:

• Days 1 to 3: expect it to be worse. Do not diagnose anything.
• Days 4 to 7: should be visibly improving. If it is, you are fine.
• Beyond a week with no improvement: now it is real, and the breakdown above will tell you which app.

One thing worth doing on day one that costs nothing: restart the phone. Not because it is magic, but because updates leave processes in odd states and a restart clears the ones that are stuck. It resolves a surprising share of post-update complaints and it is the first thing support would ask anyway.

And if you are on an older device, be honest about the alternative explanation: batteries lose capacity with age, and the update is often just when you started paying attention. The battery health figure is worth checking before blaming the software — if it has dropped a long way, no update is going to fix that.

Adding the specific things that break in an update and produce exactly your symptom, all of which are fixable in minutes.

An app stuck in a retry loop. Something that lost its credentials in the update and is now retrying in the background forever. Shows up as one app with a lot of background activity and almost no screen time. Signing out and back in fixes it; this is by far the most common real cause.

Location permissions reset to always. Updates sometimes reprompt, people tap through, and an app that used to have location only while in use now has it constantly. Worth reviewing after any major update regardless.

A settings default that changed. Background refresh re-enabled for everything, or a display setting that moved. These are silent and they add up.

Something genuinely unfinished. Photo analysis in particular can take a very long time on a large library, and it is visible — there is usually an indicator in the photos app telling you it is still working. If it says it is still processing, you have your answer directly rather than by inference.

On the downgrade question: I would not. The window is short, the process wipes the device in practice, and the overwhelming majority of these resolve either by themselves or by finding the one app above. Downgrading to fix a battery problem you have not diagnosed is a large amount of risk for a guess.