Feb 28, 2025
HTTP/2 and HTTP/3 are two different versions of the Hypertext Transfer Protocol, each designed to improve web performance and serve up features that the modern web demands: speed, security, and efficiency.
HTTP/2 introduced various interesting features, such as multiplexing and header compression. However, HTTP/3 takes things to the next level using the Quick UDP Internet Connections (QUIC) transport protocol.
Switching to QUIC improves data transmission speed and changes the game in terms of connection reliability. It's comparable to laying a robust foundation for high-performance web applications.
In this article, we'll examine what distinguishes HTTP/2 from HTTP/3 and how the introduction of QUIC influences our online experiences.
Key Differences Between HTTP/2 and HTTP/3
1. Underlying Transport Protocol
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HTTP/2: Uses the same underlying TCP (Transmission Control Protocol) as its predecessor, HTTP/1.1, and introduces features like multiplexing, header compression, and prioritization to improve TCP performance.
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HTTP/3: Uses a new transport protocol called QUIC (Quick UDP Internet Connections) instead of TCP. QUIC combines elements of TCP and UDP (User Datagram Protocol) to provide faster and more reliable connections.
2. Multiplexing
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HTTP/2: Introduces multiplexing, allowing multiple requests and responses to be sent and received simultaneously over a single TCP connection. This helps reduce latency and improves overall efficiency.
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HTTP/3: Continues to support multiplexing but does so over the QUIC transport protocol. Multiplexing in HTTP/3 can be more efficient due to the properties of QUIC.
3. Connection Setup
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HTTP/2: Requires a connection setup process known as "handshaking" to establish a secure connection using TLS (Transport Layer Security).
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HTTP/3: The QUIC protocol used by HTTP/3 incorporates security features from the start, eliminating the need for a separate TLS handshake. This can reduce connection setup times.
4. Header Compression
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HTTP/2: Implements header compression to reduce the overhead of transmitting headers in each request and response.
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HTTP/3: Also uses header compression, but it addresses issues found in HTTP/2's header compression mechanism.
5. Prioritization
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HTTP/2: Allows for prioritization of requests and responses, helping to ensure that more critical resources are loaded first.
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HTTP/3: Retains prioritization features but with some improvements over HTTP/2.
6. Flow Control
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HTTP/2: Implements flow control to manage the amount of data sent between the client and server, preventing overload and optimizing performance.
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HTTP/3: Maintains flow control, but it operates at the QUIC layer.
7. Error Handling
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HTTP/2: Relies on the underlying TCP for error handling.
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HTTP/3: Has its own error correction mechanisms within the QUIC protocol, which can speed up error recovery.
8. Transport Layer
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HTTP/2: Operates over TCP, which can sometimes suffer from head-of-line blocking issues.
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HTTP/3: Uses QUIC, which is designed to address head-of-line blocking by allowing independent streams to progress even if others are delayed.
Why Developers Are Using HTTP/3
While both HTTP/2 and HTTP/3 aim to improve web performance, HTTP/3 introduces a new transport protocol (QUIC) and addresses specific challenges found in HTTP/2, such as reducing connection setup times and mitigating head-of-line blocking issues.
HTTP/3 has become the standard protocol for development, and its adoption continues to increase as its benefits become more apparent, especially in scenarios where low latency and efficient multiplexing are crucial.
Introducing QUIC
QUIC (Quick UDP Internet Connections) is a new encrypted-by-default Internet transport protocol with several improvements designed to accelerate and secure HTTP traffic.
Google initially designed it, and the Internet Engineering Task Force (IETF) has since adopted it as a standard.
QUIC is primarily designed to address some limitations and performance bottlenecks associated with traditional transport protocols, such as TCP (Transmission Control Protocol).
Key Features
Multiplexing: Similar to HTTP/2, QUIC supports multiplexing, allowing multiple data streams to be sent and received independently over a single connection. This helps improve data transfer efficiency by reducing the latency associated with opening multiple connections.
Reduced Connection Setup Time: QUIC incorporates security features from the start, eliminating the need for a separate TLS (Transport Layer Security) handshake. This reduces the connection setup time, making it faster than the TCP and TLS combination in protocols like HTTP/2.
Header Compression: QUIC includes header compression mechanisms to reduce the overhead of transmitting headers in each request and response. This is similar to the header compression used in HTTP/2.
Improved Congestion Control: QUIC has its own congestion control mechanisms designed to adapt to network conditions and ensure efficient data transmission while avoiding congestion-related issues.
Error Correction: QUIC includes built-in error correction mechanisms, allowing faster recovery from packet loss or other network issues. This contrasts with relying on the underlying transport protocol (such as TCP) for error recovery.
Low Latency: QUIC is designed to reduce latency by addressing issues such as head-of-line blocking, where the delay of one packet can affect the delivery of subsequent packets. This is achieved by allowing independent streams to progress even if others are delayed.
Flexibility: QUIC is not tied to a specific application and can be used as a general-purpose transport protocol. It has been adopted as the underlying transport protocol for several applications, including HTTP/3.
Connection Migration: QUIC allows for seamless connection migration, enabling a client to switch between different network interfaces (such as Wi-Fi and cellular) without interrupting the ongoing communication.
Wrapping Up
QUIC has gained significant attention and adoption. It is well-suited for low latency, quick connection setup, and efficient multiplexing scenarios, making it ideal for applications such as web browsing, streaming, and other real-time communication protocols.
At Oshyn, we have long embraced the HTTP/3 protocol for all our applications. This allows us to create robust, secure solutions and give website visitors the best experience. Contact us if you want to upgrade your digital presence using HTTP/3 and a leading digital experience platform like Adobe, Sitecore, or Optimizely. We can help.
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