Measurment Platform

Our measurements run in three phases:

• Phase I: Workers on PlanetLab probe a list of sites based on the top 1 million Alexa sites (see below), using NPN and ALPN to determine which sites announce HTTP/2 support. (Runs daily.)
• Phase II: Workers in our labs in Cleveland, USA and Barcelona, Spain attempt to fetch the root object for each site that claims to support HTTP/2. The result is a list of sites that partially and truly support HTTP/2. (Runs daily.)
• Phase III: Crawlers in Barcelona, Cleveland, and Pittsburgh fetch each site that actually supports HTTP/2 using HTTP/1.1 and HTTP/2 and records performance and usage information like page load time and number of TCP connections used. (Runs weekly.)

We use the Alexa Top 1 Million list. From November 2014 to August 2015, we use a copy of the Alexa list fetched on November 10th, 2014. Beginning in September 2015, we merge the current Alexa list with our own each day, constantly expanding the pool of sites we query: