How to Fix a Phone That Got Slow After an Update

Published 2026-10-16 · Marion Phone Repair

The phone was fine yesterday. Then a software update installed, and now everything is sluggish — apps take longer to open, the keyboard lags behind typing, scrolling stutters, and the whole phone feels like it aged five years overnight. This is one of the most common complaints after both iOS and Android updates, and it is almost always temporary or fixable. The update itself is rarely the long-term problem — it is what happens in the hours and days after the update that causes the slowdown.

Why phones slow down after updates

Understanding the cause helps you decide whether to wait it out or take action:

Background optimization

After a major update, the phone reindexes all files, recompiles app caches, rebuilds search databases, and optimizes storage. On Android, this shows as Optimizing apps during the first boot after updating. On iPhone, the indexing happens silently in the background. This process can keep the CPU and storage busy for hours — sometimes 24 to 48 hours on phones with a lot of data. During this time, everything else competes for resources and runs slower.

New features using more resources

Major OS updates often add features that consume more memory, CPU, or battery than the previous version. AI-powered features, enhanced photo processing, new visual effects, and expanded background services all add load. Older phones with less RAM and slower processors feel this more than newer ones.

App incompatibility

After an OS update, some apps may not be fully compatible with the new version yet. The app still runs but performs poorly — crashing, leaking memory, or using excessive CPU while it tries to operate with APIs that have changed. App developers typically release compatibility updates within days to weeks of a major OS release.

Cached data from the old version

Apps and the system itself cache data optimized for the previous OS version. After an update, this cached data may be incompatible or corrupt, forcing the system to work around it rather than using it efficiently. Clearing caches resolves this.

Fix 1: Wait 24 to 48 hours

If the update just installed (within the last day), give the phone time to complete background optimization. Keep the phone plugged in and connected to Wi-Fi overnight — many optimization tasks only run when the phone is charging and idle. Check performance the next morning. If the phone is noticeably faster, the optimization was the bottleneck and no further action is needed.

Fix 2: Restart the phone

A restart after an update clears temporary data, resets all running processes, and often completes pending optimization steps that are stalled:

Fully power off the phone (not just sleep), wait 30 seconds, and power it back on
If you have not restarted since the update installed, this single step can make a significant difference. Some updates do not fully take effect until the next clean restart

Fix 3: Update all apps

After an OS update, check for app updates immediately. Developers release compatibility updates alongside major OS releases:

iPhone: Open the App Store, tap your profile icon, scroll down to see available updates, and tap Update All
Android: Open the Google Play Store, tap your profile icon, Manage apps and device, Update all

An app that was optimized for the previous OS version may run poorly until its compatibility update is installed. Social media apps, banking apps, and games are the most commonly affected.

Fix 4: Clear cached data

Android

Clear app caches individually: Settings, Apps, select an app, Storage, Clear cache. Focus on apps that feel the slowest — browser, social media, email. Clearing the cache forces the app to rebuild its cached data for the new OS version
Clear system cache partition: Power off the phone. Hold Volume Up + Power (the combination varies by manufacturer) to boot into Recovery Mode. Use the volume buttons to navigate to Wipe cache partition and press Power to select it. This clears the system-level cache without affecting personal data. Not all phones still offer this option in newer Android versions

iPhone

iOS does not have a manual cache-clearing option at the system level. Offloading and reinstalling individual apps clears their cached data: Settings, General, iPhone Storage, select an app, Offload App, then reinstall it from the App Store. Focus on apps that are using the most storage, as they have the largest caches.

Fix 5: Free up storage space

A phone with storage that is more than 90 percent full runs slower than one with free space. Both iOS and Android need free storage for swap files, caches, and temporary data during normal operation. After an update, the OS may use additional storage for optimization files:

Check available storage: Settings, General, iPhone Storage (iPhone) or Settings, Storage (Android)
Delete old photos and videos that are backed up to the cloud. Photos and videos are usually the largest storage consumers
Delete apps you no longer use. Many phones accumulate dozens of apps that have not been opened in months
Clear message attachments. Group chats with years of photos and videos can consume gigabytes
Aim for at least 10 to 15 percent free space for smooth operation

Fix 6: Disable new features you don't need

Major updates often enable new features by default that consume resources. Common ones to check:

Visual effects and animations. On Android, Settings, Developer options (tap Build number 7 times to enable), scroll to Window animation scale, Transition animation scale, and Animator duration scale. Setting these to 0.5x or Off makes the phone feel faster by reducing animation time. On iPhone, Settings, Accessibility, Motion, Reduce Motion
Background app refresh. New updates sometimes reset this setting. Check Settings, General, Background App Refresh (iPhone) or Settings, Apps, each app's battery settings (Android). Disable for apps that do not need real-time updates
Live wallpapers and widgets. Animated wallpapers and complex widgets with frequent refresh intervals consume CPU and battery. Switch to a static wallpaper and remove widgets you do not actively use
AI and smart features. Recent updates add AI-powered suggestions, smart text selection, live captions, and similar features that run continuously. Disable any you do not use — each one runs a background service

Fix 7: Check battery health

Phones with degraded batteries may throttle CPU speed after an update to prevent unexpected shutdowns. This is especially true for iPhones — iOS includes a performance management feature that reduces CPU speed when the battery can no longer deliver peak power:

iPhone: Settings, Battery, Battery Health and Charging. If Maximum Capacity is below 80 percent and Peak Performance Capability shows a message about performance management, the phone is being throttled. A battery replacement restores full performance
Android: Settings, Battery, Battery health (Samsung, Pixel). Third-party apps like AccuBattery can estimate battery wear on other Android brands

Fix 8: Factory reset (last resort)

If the phone is still slow after trying everything above and waiting several days, a factory reset installs the new OS version cleanly without carrying over any corrupt data or incompatible settings from the old version:

Back up everything first — photos, contacts, messages, app data
iPhone: Settings, General, Transfer or Reset iPhone, Erase All Content and Settings. Restore from backup after setup, or set up as a new phone for the cleanest result
Android: Settings, General management, Reset, Factory data reset. Restore from Google backup after setup

Setting up as a new phone (rather than restoring a backup) eliminates any corrupt settings or data from the old installation but requires reinstalling apps and reconfiguring settings manually. It produces the best performance but is the most work.

Speed diagnosis in Marion

Marion Phone Repair diagnoses phones that slowed down after updates — identifying whether the cause is background optimization, battery throttling, storage pressure, or a hardware limitation, and applying the targeted fix.