The Navigation Timing API provides useful data that can be used to measure the performance of a website. Unfortunately this API has never been good at capturing the actual user experience.
The Speed Index, introduced by WebpageTest.org, aims to solve this issue. It measures how fast the page content is visually displayed. The current implementation is based on the Visual Progress from Video Capture calculation method described on the Speed Index page. The visual progress is calculated by comparing the distance between the histogram of the current frame and the final frame.
Before using speedline
, please install ImageMagick and ensure that your version of node is greater than 5.0
.
$ npm install -g speedline
Note: You should enable the
screenshot
options before recording the timeline.
$ speedline --help
Usage
$ speedline <timeline> [options]
Options
-p, --pretty Pretty print the output
Examples
$ speedline ./timeline.json
By default the CLI will output the same output as visual metrics. You can use the --pretty
option if you want to have the histogram.
MIT © Pierre-Marie Dartus