Build resilient systems at scale
October 12–14, 2015 • New York, NY

HTTP/2 vs. HTTP/1.1: A performance analysis

Ragnar Lonn (Load Impact), Daniel Stenberg (Mozilla)
1:15pm–1:55pm Tuesday, 10/13/2015
Location: Regent Parlor
Average rating: ***..
(3.74, 19 ratings)
Slides:   external link,   external link

Prerequisite Knowledge

Attendees with a basic understanding of HTTP, TCP, and web performance will learn a lot from this presentation, including how to use the new HTTP/2 testing tool developed by Stenberg and Load Impact.


HTTP/2 is about to happen – most major browser and server makers are working on support for HTTP/2, and some, like Firefox, already have it enabled by default. The protocol is backward-compatible with HTTP/1.1 and is likely to suddenly become ubiquitous, when new versions of clients and servers switch it on. But the web development community is still largely ignorant about HTTP/2 and what it means for their applications.

In this talk we will present the results of a new study by Ragnar Lönn, founder of Load Impact, and Daniel Stenberg, founder of curl and libcurl and active contributor to the HTTPbis working group within the IETF focusing on HTTP/2 specification. We’ll attempt to measure the performance impact different types of applications might typically get if they switch their data transport from HTTP/1.1 to HTTP/2.

In the study, we emulated different HTTP application types while communicating with the application back ends, over first HTTP/1.1 and then HTTP/2, in order to find out how much performance and/or user-experience differed between the two protocols. We set up a test bed where we could, under controlled conditions, simulate different use cases, in terms of the number of concurrently used objects and object size/weight, in order to cover everything from the “REST API” scenario to the “classic web page” scenario. We also simulated different network characteristics to capture the user experience impact of different types of internet connections – particularly mobile connections – that experience high network delay.

As an extra treat we will also release the software created as part of the study, as a free online tool that anyone can use to find out what happens performance-wise if their site or application is delivered over HTTP/2 instead of HTTP/1.1.

The tool is very simple to use – just enter the URL of your site and click a start button, and it will provide detailed information on what kind of performance improvement, if any, your particular app would get by switching to HTTP/2. Conference attendees will be the first to see this tool, which will be live and available to the world immediately after the speaker session.

Photo of Ragnar Lonn

Ragnar Lonn

Load Impact

Ragnar Lönn is founder and CEO of Load Impact, the world’s most popular online load-testing service for testing the performance of websites. Load Impact users have executed over 300,000 load tests since 2009. Previously, Ragnar worked in the ISP industry and founded one of Sweden’s first Internet service providers, Algonet, in 1994. His more unexpected interests include running, macroeconomics, and energy-storage technologies.

Photo of Daniel Stenberg

Daniel Stenberg


Daniel Stenberg (, employed by Mozilla, is perhaps most known as the founder and main developer of curl and libcurl. He’s been working with internet protocols for almost 20 years, and has been actively involved in the HTTPbis working group within the IETF during the HTTP/2 specification work. Daniel is involved with several different HTTP/2 implementations, and is the author of perhaps the most exhaustive HTTP/2 document available, http2 explained.

Comments on this page are now closed.


Picture of Alexander Sommer
Alexander Sommer
10/21/2015 3:23am EDT

The download of the slides is not working

Picture of Daniel Stenberg
10/20/2015 11:05pm EDT

Sorry, but if the file still fails (it is the part1 as a PDF), the two presentation parts are also available here:

part 1:

part 2:

Ronak Rathod
10/20/2015 7:21pm EDT

Hi Daniel,
I am not able to open the bin format for the slideshow. Would you mind sharing the PDF/PPT for the slides?

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