Cloudflare Cloudflare Comparing HTTP/3 vs HTTP/2 Performance

eva2000 · Apr 14, 2020

New blog article Comparing HTTP/3 vs. HTTP/2 Performance

Even though HTTP/3 is still in draft status, we've seen a lot of interest from our users. So far, over 113,000 zones have activated HTTP/3 and, if you are using an experimental browser those zones can be accessed using the new protocol! It's been great seeing so many people enable HTTP/3: having real websites accessible through HTTP/3 means browsers have more diverse properties to test against.

When we launched support for HTTP/3, we did so in partnership with Google, who simultaneously launched experimental support in Google Chrome. Since then, we've seen more browsers add experimental support: Firefox to their nightly builds, other Chromium-based browsers such as Opera and Microsoft Edge through the underlying Chrome browser engine, and Safari via their technology preview. We closely follow these developments and partner wherever we can help; having a large network with many sites that have HTTP/3 enabled gives browser implementers an excellent testbed against which to try out code.
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Benefits
One of the main touted advantages of HTTP/3 is increased performance, specifically around fetching multiple objects simultaneously. With HTTP/2, any interruption (packet loss) in the TCP connection blocks all streams (Head of line blocking). Because HTTP/3 is UDP-based, if a packet gets dropped that only interrupts that one stream, not all of them.

In addition, HTTP/3 offers 0-RTT support, which means that subsequent connections can start up much faster by eliminating the TLS acknowledgement from the server when setting up the connection. This means the client can start requesting data much faster than with a full TLS negotiation, meaning the website starts loading earlier.
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Synthetic benchmarks are interesting, but we wanted to know how HTTP/3 would perform in the real world.

To measure, we wanted a third party that could load websites on our network, mimicking a browser. WebPageTest is a common framework that is used to measure the page load time, with nice waterfall charts. For analyzing the backend, we used our in-house Browser Insights, to capture timings as our edge sees it. We then tied both pieces together with bits of automation.

As a test case we decided to use this very blog for our performance monitoring. We configured our own instances of WebPageTest spread over the world to load these sites over both HTTP/2 and HTTP/3. We also enabled HTTP/3 and Browser Insights. So, every time our test scripts kickoff a webpage test with an HTTP/3 supported browser loading the page, browser analytics report the data back. Rinse and repeat for HTTP/2 to be able to compare.
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Cloudflare Cloudflare Comparing HTTP/3 vs HTTP/2 Performance

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