Understanding the differences between HTTP/2 and HTTP/3

Through our SEO Agency Optimize 360

HTTP/2 and HTTP/3

In today's fast-moving world, website performance has become a major challenge if we are to offer the best possible service. user experience quality.

It was in this context that the HTTP/2 and HTTP/3 protocols were developed.

But what do these terms really mean and what are the differences between them?

In this article, we'll take a closer look at the main features of each of these protocols.


HTTP/2 and HTTP/3

1. The origin of HTTP/2

The protocol HTTP/1.1 has been the standard since 1997However, it had certain limitations and performance problems. To overcome these shortcomings, the HTTP/2 protocol was developed by the IETF (Internet Engineering Task Force) and made official in 2015. Using SPDY, another protocol developed by Google, as its technological base, HTTP/2's main objective was to improve performance.

2. Improvements brought by HTTP/2

Thanks to a number of technical innovations, HTTP/2 has resolved some of the problems inherent in HTTP/1.1 :

  • Request multiplexing : Unlike HTTP/1.1, where each request had to be processed separately, HTTP/2 enables several requests to be processed at the same time within a single TCP connection, thereby reducing latency.
  • Header compression : To minimise protocol overhead, HTTP/2 compresses request and response headers using the HPACK algorithm.
  • Prioritising requests : The protocol allows you to define priorities for different resources, so that those that are essential for page layout are loaded first.

3. Deploying HTTP/2

Since its official launch in 2015, HTTP/2 is now widely adopted by web servers and browsers, thanks in particular to its backward compatibility with HTTP/1.1. This means that even if a browser or server does not yet support HTTP/2, it can still communicate using the old protocol.

4. The emergence of HTTP/3

After HTTP/2, the web world continued to evolve and new performance and security requirements emerged. The IETF therefore launched work on a new protocol, HTTP/3, based on QUICan experimental protocol developed by Google.

5. The advantages of HTTP/3 over its predecessors

HTTP/3 offers several significant improvements over HTTP/2 :

  • Change of protocol : Whereas HTTP/2 used the TCP protocol, HTTP/3 is built on QUIC, which uses UDP (User Datagram Protocol). This transition avoids certain problems associated with congestion and packet loss.
  • Reduced latency : One of the main improvements offered by HTTP/3 is a significant reduction in latency thanks to the switch to QUIC, particularly during connection establishment and in environments where packet loss is frequent.
  • Migration between IP addresses : With QUIC, it is possible to maintain an active connection even if the IP address of the client or server changes, which can make it easier to manage mobile connections or network changes.

6. The challenges posed by HTTP/3

Despite its advantages, HTTP/3 also faces a number of challenges:

  • Compatibility : Unlike HTTP/2, HTTP/3 is not backward-compatible with HTTP/1.1, which can cause difficulties when it comes to deployment and support by browsers and web servers.
  • Interoperability with existing systems: Switching from TCP to UDP can lead to interoperability problems with certain network infrastructures and equipment that do not support this protocol.
  • Performance : Although QUIC offers a number of performance benefits, it is not yet clear whether these gains will translate into significant improvements for all users and in all situations.

7. Deploying HTTP/3

Development of the HTTP/3 protocol is still underway, but several browsers and web servers have already started to support itincluding Google Chrome and Firefox. The specification was approved in November 2020, and we can expect its adoption to increase gradually as market players integrate it into their products and services.

8. HTTPS, enhanced security

It is important to remember that the improvements made by HTTP/2 and HTTP/3 are not just about performance, but also about security. This is because, these protocols are often combined with SSL/TLS to secure exchanges between the client and the server (known as HTTPS). In particular, using HTTPS helps to prevent attacks through espionage, falsification or identity theft.

9. Risks associated with the deployment of new protocols

Although the move to HTTP/2 and HTTP/3 has many advantages, it is not without risks:

  • Increased complexity : Managing connections and resources is becoming more complex with the introduction of new features such as multiplexing, prioritisation and encrypted connections.
  • Compatibility : The adoption of new protocols can lead to compatibility problems between different browsers, servers and network equipment, particularly if HTTP/3 is not backward compatible with HTTP/1.1.
  • Safety : Switching to HTTPS requires particular attention to the configuration and management of SSL/TLS certificates to ensure an adequate level of security.

10. Future prospects

With the advent of HTTP/2 and HTTP/3, the HTTP protocol continues to adapt to the changing needs of the web. Although it is still too early to determine the real impact of HTTP/3 on performance and user experience, it is clear that these innovations offer new opportunities to improve the speed, reliability and security of websites and online applications.

blank Digital Performance Accelerator for SMEs