Duration:
RAF: FPS:
CPSF:

A few words of introduction

The goal of this page is to monitor frame rate while scrolling. As you would expect, the jank checkbox introduces random jank via javascript.

Most mobile browsers handle scrolling off thread, as well as some desktop browsers. In those systems, onScroll fires after the scroll happens, and it is typically throttled, making it very hard to determine the actual quality-of-experience taht the user is having. Moreover, even though when a user is scrolling, we may want to measure FPS, when the user isn't scrolling [happens way more often!] we dont' want to be burning CPU cycles on our measurement harness. A good FPS monitoring API should report the smoothness of this page when scrolling, and leave the CPU completely idle otherwise. An even better monitoring API will tell us how often the main thread is able to participate in the frames, so that the quality of any scroll-coupled effects (eg hidey bars) can be monitored.

And now for some gratuituously repeated letters!

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