Why is my new phone slower than my old one?
A newer phone can genuinely feel worse than the one it replaced. The usual causes are background apps, a full disc, thermal state and an ageing battery — and most of them are visible in a benchmark if you know what to look at.
This is a real thing, not a trick of memory, and there are only a handful of causes. Most of them are fixable, and most of them show up clearly in a measurement.
It may not be slower — it may be less smooth
People describe stutter as slowness, and the two are different. A phone that renders 60 frames a second and drops one every few seconds feels worse than a phone that renders 45 evenly. Average frame rate cannot tell these apart; the 1% low can, because it is the mean of the slowest frames rather than of all of them.
If a device shows a healthy average but a 1% low far beneath it, you are feeling stutter, not lack of power. That points at software — something interrupting — rather than at the hardware.
Background apps are the usual culprit
A phone that has been in use for a year is running far more in the background than the day it came out of the box: sync services, chat apps, widgets, location updates. Each one takes a slice of CPU and a slice of memory, and on a phone with less memory the system starts evicting whatever you were just using, so returning to an app reloads it from scratch.
This is the first thing to rule out. Close everything, run the test, then reboot and run it again. A large gap between the two says background load, not hardware.
A nearly full disc slows everything down
Flash storage gets slower as it fills, because the controller has fewer free blocks to write into and has to shuffle existing data first. The effect is modest until you are near capacity and then it is severe. If a device is above about 90% full, free some space before concluding anything about it.
Heat, and the battery underneath it
Sustained work makes a phone hot, and a hot phone deliberately slows down to protect itself. This is normal and every phone does it — what varies is how quickly it starts and how far it drops. A phone in a thick case, in sunlight, or charging while you use it, will throttle sooner.
An ageing battery has a related effect that surprises people: as a cell wears, it cannot deliver current in the short bursts a fast processor demands, so the system caps the processor to stay within what the battery can supply. The phone is not broken and the chip is fine — it is being held back by the cell.
What makes a device throttle goes into how this shows up in a measurement.
Software genuinely got heavier
The version of the operating system your phone shipped with is not the version it is running now. Interfaces gain animations, effects and higher-resolution assets over time, and apps do the same. A phone that felt instant on launch software can feel laboured on software written for the generation after it, without a single component having degraded.
A higher refresh rate screen makes this more visible, not less: at 120 Hz the device has 8 milliseconds to produce each frame instead of 16, so the same hesitation that passed unnoticed becomes a visible stutter.
What a browser test can and cannot see
It can measure how much work the processor gets through, how evenly frames arrive, how bad the worst frame was, and whether the result changes between passes. It can show that a device is performing below what its own silicon normally achieves — which is the most useful signal here.
It cannot see your storage, read your battery’s health, or measure temperature: no browser exposes any of those. Anything claiming to show you a phone’s temperature in a web page is drawing a picture.
A practical order to work through
- Close background apps and reboot.
- Check free storage; clear space if it is above roughly 90% full.
- Let the phone cool, take it out of its case, and unplug it.
- Run the test and note the 1% low and the pass spread, not just the average.
- Test the old phone too, and compare the two results directly.
Measure the device you are holding
About a minute, nothing installed, and it works on a device you do not own.
Run the test