Overview
It's common for a phone to feel slower or warmer for a day or two after a big update — and it's usually nothing to worry about. Behind the scenes the system is re-optimising apps and rebuilding caches, which uses the processor and generates heat. This guide explains what's happening, how to help it settle, and what to try if it doesn't improve after a few days.
Symptoms you might see
- The phone feels laggy or stutters right after an update.
- It runs warm even when you're not doing much.
- The battery drains faster than usual for a day or two.
- Apps are slow to open the first time after the update.
Possible causes
- The system is re-optimising apps and rebuilding caches in the background.
- Search indexing and backups re-run after a major update.
- An individual app needs its own update to run well on the new software.
- A settings change from the update increased background activity.
Step-by-step troubleshooting
Work through these in order — the earliest steps are the safest and fix the most cases.
-
Give it 24–48 hours
The post-update background work — re-optimising apps, rebuilding caches, re-indexing — is temporary and heavy. For most phones, speed and temperature return to normal within a day or two of normal use. Charge it and be patient first.
-
Restart the phone
A clean restart clears stuck background processes left over from the install. Power off fully, wait a few seconds, and power back on. This alone resolves a lot of 'slow after update' complaints.
-
Update your apps
Open your app store and update everything. Apps often need their own update to run smoothly on new system software; an out-of-date app is a common cause of lag or heat after a system update.
-
Find a misbehaving app
Open Settings, Battery and check the usage list. If one app is suddenly using far more power or running constantly in the background, update it, force-stop it, or reinstall it. A single runaway app can keep the phone warm and slow.
-
Let it cool and ease the load
If it's hot, take any thick case off, keep it out of the sun, and avoid heavy gaming or recording until it settles. Lower screen brightness and close demanding apps while the system finishes its background work.
-
Clear cache or seek help if it persists
If it's still slow after several days, clear the cache of the worst-offending apps in Settings, Apps. If performance or heat remains clearly worse than before the update with no single app to blame, note your model and patch date and contact us or a qualified technician.
Before you go further: back up your device to a cloud backup or a computer whenever possible. Steps that could affect your data are clearly flagged — and for suspected hardware faults, a qualified repair professional is the safest next step.
Prevention tips
- Expect a short settling-in period after any major update.
- Keep apps updated so they match the new system software.
- Restart the phone once after a big update to clear leftover processes.
- Avoid heavy tasks for the first day while background work finishes.
- Maintain some free storage so re-optimisation has room to work.
Frequently asked questions
Is it normal for a phone to be slow after an update?
Yes, for a day or two. The system re-optimises apps and rebuilds caches in the background after a major update, which temporarily uses the processor and can cause lag and warmth. It usually settles on its own.
How long until it goes back to normal?
Most phones feel normal again within 24–48 hours of regular use. A restart and updating your apps can speed that up. If it's still worse after several days, dig into the battery usage list for a problem app.
Can I undo an update that slowed my phone?
Rolling back system updates generally isn't supported and isn't advisable, since it reopens security holes. Focus instead on letting it settle, updating apps, and finding any single app causing the slowdown.
Related guides
FixSupport is an independent educational resource and is not affiliated with, endorsed by, or sponsored by any phone manufacturer or software maker. Our guides provide general information only; for physical or hardware faults we recommend a qualified local technician. All product names and trademarks belong to their respective owners.