Last month, I found my old Samsung Galaxy S21 (2021 model) sitting at the back of a drawer. Out of curiosity, I turned it on to see if it could still function as a backup device.
The experience was rough.
Swiping through the home screen felt sluggish, opening the camera took several seconds, and even switching between apps caused noticeable stutters. It was clear that the phone, despite once being a flagship device, was struggling to keep up with modern apps and background processes.
I chose to take the experiment seriously instead of replacing it right away. I used the phone as my secondary daily device for one full week, testing different optimization methods to see which ones actually improved performance.
Rather than relying on common “phone booster” myths, I focused on practical system tweaks, storage management, and built-in Android tools.
Some methods made a surprisingly large difference, while others turned out to be completely useless.
Here’s what actually worked.
Why Older Android Phones Slow Down
Before testing any fixes, it helps to understand why phones slow down over time.
Most performance issues come from three common causes:
1. Storage congestion
Modern smartphones use fast storage technology, but performance can drop when the device becomes nearly full. When storage reaches high usage levels, the system struggles to manage temporary files and background processes efficiently.
2. Background services
Newer apps often run multiple background services such as notifications, syncing, analytics, and location tracking. These consume both RAM and CPU resources.
3. Heat and throttling
When a phone gets too warm, the processor automatically reduces its speed to protect internal components. This behavior is called thermal throttling, and it can make devices feel slow during heavy use.
To see how much these factors mattered, I started with a quick baseline of my device.
Test Device Specifications
Device: Samsung Galaxy S21
Processor: Exynos variant
RAM: 8GB
Storage: 128GB
Storage Used: 92% at the start of testing
Operating System: Android 14 (One UI 6.1)
At nearly full storage capacity and after years of updates, the phone had accumulated plenty of digital clutter.
Method 1: Reducing Animation Speed
One of the most commonly recommended Android tweaks involves adjusting animation scales inside Developer Options.
Animations control how quickly windows open, apps switch, and menus appear. Slowing them down makes the system less responsive.
What I did
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Enabled Developer Options by tapping Build Number seven times.
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Opened Developer Options in Settings.
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Reduced these values from 1.0x to 0.5x:
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Window animation scale
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Transition animation scale
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Animator duration scale
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Result
The change doesn’t increase processor speed, but it reduces the time spent rendering animations. As a result, the phone feels noticeably quicker when navigating the interface.
Verdict
Recommended:
It’s a quick tweak that improves perceived responsiveness without affecting battery life.
Method 2: Clearing the System Cache
Many users regularly clear their app caches, but few know that Android also stores a system cache partition.
This cache contains temporary files created during software updates and system operations.
What I did
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Powered off the phone.
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I connected the phone to a PC via USB.
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I entered Recovery Mode by pressing Power + Volume Up.
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Selected Wipe Cache Partition.
Result
After rebooting, small interface stutters became less frequent, especially when opening the notification panel or switching settings menus.
Verdict
This method is beneficial for reducing minor system lag.
This doesn’t dramatically speed up apps but can make the operating system feel smoother.
Method 3: The 20% Storage Rule
This turned out to be the most important fix.
Modern flash storage slows down when it approaches full capacity. At the start of testing, my phone’s storage was 92% full, leaving very little space for system operations.
What I did
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Deleted 40GB of old video files
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Uninstalled several unused games
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Removed duplicate photos and downloads
This reduced storage usage from 92% to about 60%.
Result
The difference was immediate.
Apps installed faster, gallery thumbnails loaded smoothly, and the phone stopped freezing when scrolling through large photo collections.
Verdict
Essential:
If your phone’s storage is above 85%, freeing space can significantly improve performance.
Method 4: Disabling Background Tracking Features
Many built-in Android services quietly track usage data or listen for voice commands.
Two common examples include:
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Digital Wellbeing
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Google Assistant voice activation
What I did
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Revoked Usage Access from Digital Wellbeing
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Disabled the “Hey Google” voice trigger
Result
RAM usage dropped slightly, and the phone ran a bit cooler during extended use.
Battery life also improved slightly during daily use.
Verdict
Small improvement.
While it’s not a significant improvement, it does contribute to the reduction of unnecessary background activity.
Method 5: Replacing Heavy Apps with Web Versions
Many social media apps have become extremely resource-heavy.
Apps like Facebook or Instagram run multiple background services that consume RAM and battery.
What I did
Instead of installing the full apps, I used Progressive Web Apps (PWAs):
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Opened the mobile website in Chrome.
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Selected:: Add to Home Screen.
Result
Idle RAM usage dropped significantly, and the phone stayed cooler during extended browsing.
For older devices with limited memory, this change alone can make the system feel far more stable.
Verdict
This change is highly effective for older hardware.
Method 6: Testing “Phone Booster” Apps
Out of curiosity, I also tested several highly rated RAM cleaner apps from the Play Store.
What I did
I installed three popular optimization tools and utilized their “boost” features.
Result
The outcome was disappointing.
These apps constantly ran in the background, consumed additional CPU cycles, and displayed ads. In some cases, the phone actually felt slower after installing them.
Android’s built-in memory management is already optimized, so external cleaners often interfere rather than help, leading to decreased performance and user frustration.
Verdict
Avoid entirely.
Method 7: The Factory Reset (The Nuclear Option)
After four years of system updates and app installations, a smartphone accumulates a large amount of leftover data.
Old folders, broken settings, and unused files can gradually affect system stability.
What I did
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I backed up important files on Google Drive.
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I carried out a factory data reset.
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Reinstalled only essential apps.
Result
This made the biggest overall difference.
The phone felt much closer to how it performed when it was new. Apps launched faster, system heat decreased, and the overall experience became smoother.
Verdict
Although it is the most powerful solution, it takes time to reinstall apps and restore data.
Performance Summary
| Method | Impact | Difficulty | Risk |
|---|---|---|---|
| Animation adjustments | Improves perceived speed | Easy | None |
| Freeing storage | Major performance gain | Medium | None |
| Factory reset | Largest improvement | Hard | Data loss risk |
| Cache partition wipe | Reduces stutters | Medium | Low |
| Lite web apps | Improves RAM usage | Easy | None |
| Booster apps | Negative impact | Easy | High |
Additional Android Maintenance Tips
During testing, I also discovered a few smaller tweaks worth checking.
Check Google Play System Updates
Many users only install regular Android updates, but updates to the Google Play system often include security patches and driver improvements.
Disable Virtual RAM (If Available)
Some devices include a feature that uses storage as extra RAM. On older phones with slower storage, disabling this option may improve responsiveness by reducing the load on the device’s storage and allowing the system to allocate resources more efficiently.
Review Auto-Start Apps
Some apps automatically start when the phone boots. Limiting unnecessary auto-start permissions can reduce background load.
Frequently Asked Questions
Does replacing the battery make a phone faster?
Indirectly, yes. A degraded battery may limit how much power the processor receives, which can cause the system to reduce CPU speed for stability.
How much free storage should a phone have?
Keeping 15–20% of storage free allows Android to manage background tasks and temporary files more efficiently.
Are custom ROMs still useful in 2026?
For experienced users, installing a lightweight custom ROM, which is a modified version of the Android operating system,, which is a modified version of the Android operating system, can extend the life of older devices. However, some banking apps and security services may not work on modified systems, which can limit the usability of custom ROMs for users who rely on these applications for financial transactions and security.
Do task killer apps help performance?
Generally no. Android is designed to manage memory automatically, and external task killers often create more problems than they solve.
Is it worth fixing an older phone instead of buying a new one?
If the hardware is still functional, simple optimizations, such as clearing cache, uninstalling unused apps, and updating the operating system,, such as clearing cache, uninstalling unused apps, and updating the operating system, can often extend a phone’s usability for several more years.
Final Thoughts
After a week of testing, my old Galaxy S21 became surprisingly usable again.
The combination that worked best was
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freeing storage space
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switching to lightweight web apps
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performing a factory reset
Together, these changes removed years of accumulated clutter and reduced background loads on the system.
While older smartphones will never match the speed of the newest models, they can often remain reliable devices with a little maintenance.
Sometimes the solution isn’t buying a new phone—it’s simply giving the old one a proper cleanup.