samccone / speedline

Calculate the speed index and visual performance metrics from chrome dev tool timeline

speedline

Background

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.

Install

Before using speedline, please install ImageMagick and ensure that your version of node is greater than 5.0.

$ npm install -g speedline

CLI

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.

License

MIT © Pierre-Marie Dartus