Note: I limited the height of the Y-axis to 500 milliseconds to keep the middle of the graph from getting compressed too much. The 99th-percentile time was over 16 seconds. (A logarithmic scale wouldn’t work well for this data set because the first 10% of the Y-values on the left side of the graph were zeros.)
The median time spent waiting for client-side processing was slightly over 50 milliseconds. In an absolute sense, 50 milliseconds is a nontrivial amount of time; it’s on the same order of magnitude as the first-byte response time for a lot of the HTTP requests in this same data set. In relative terms, though, the client-side time was only a single-digit percentage of total page load time (measured from the first HTTP request to the
onLoad event) for almost all of the websites in the sample:
Subjectively speaking, the amount of time spent on the client side is:
- Larger than I expected,
- Still not big enough to be the primary performance bottleneck for most websites,
- But worth checking when doing website performance optimization work.