# Scroll Performance Test

> Auto-scrolls a sample panel at a constant speed and counts dropped frames, so you can see how smooth this device really is.

URL: https://uttir.com/scroll-performance-test
Categories: web-tools, developer-tools
Privacy: The test runs entirely in your browser. Frame timings are measured locally and never sent anywhere.

## About

Scrolling is the most common sustained rendering work a browser does, which makes it a good stress-free probe of device smoothness. This test auto-scrolls a sample panel at a constant speed for eight seconds, timestamps every frame, and reports the average frame rate plus the percentage of "long frames" — frames that took noticeably longer than the median.

A healthy device scrolls with a long-frame ratio near zero percent. A few percent is normal on busy systems; a double-digit ratio is what your eyes register as stutter, and it usually means background work, an overloaded page, or thermal throttling is stealing time from rendering.

Because the workload is identical every run, the test is repeatable: re-run it after closing background apps, clearing storage pressure, or letting a hot device cool down, and compare.

## How to use

1. **Keep the tab visible** — Background tabs are frame-throttled, which would fake a bad score.
2. **Start the test** — The panel scrolls by itself for eight seconds — no input needed.
3. **Read the jank ratio** — Average FPS plus the percentage of long frames tell you how smooth the device is.

## Examples

### Score guide

Interpreting the long-frame ratio.

Output:

```
Near 0%: smooth. 1-5%: mostly smooth with occasional stumbles. Above 10%: clearly noticeable stutter — check background load and thermals.
```

## FAQ

### Why auto-scroll instead of letting me scroll?

Human scrolling varies in speed and pauses, which makes runs impossible to compare. Constant-speed scrolling makes the workload identical every time, so before/after comparisons are meaningful.

### What causes long frames?

Anything that blocks or delays rendering: heavy background scripts, large layout work, thermal throttling on hot devices, or the browser loading other tabs and extensions.

### My desktop scores great but my phone does not — why?

Mobile devices trade peak performance for battery and thermals. Sustained work loads trigger throttling faster, which shows up as a higher long-frame ratio. That is exactly what this test surfaces.

### How is this different from the FPS benchmark?

The FPS benchmark measures the idle rendering rhythm of your display. This test adds continuous rendering work (scrolling) and reports how often frames miss their slot under load.

## Related tools

- [FPS Benchmark](https://uttir.com/fps-benchmark) — Measure your display's real refresh rate and frame delivery stability in a 10-second test.
- [Reaction Time Test](https://uttir.com/reaction-time-test) — Measure your visual reaction time in milliseconds over five rounds, with a median score and per-trial breakdown.

---

For the full HTML page with the live tool, visit https://uttir.com/scroll-performance-test.
This file is the markdown rendering at https://uttir.com/scroll-performance-test.md. See https://uttir.com/llms.txt for a site-wide summary.