HTTP is the protocol that enables communication between clients and servers on the World Wide Web. It has different versions that have evolved over time to improve the performance and security of data transmission. The main versions of HTTP are:
- HTTP/1.x: The first version of HTTP, introduced in 1991 and revised in 1996 and 1999.
- HTTP/2: The second version of HTTP, standardized in 2015.
- HTTP/3: The third version of HTTP, still under development.
HTTP is a key topic in web development and web performance optimization. Understanding the differences between the versions of HTTP can help you choose the best option for your applications and users.
HTTP/1.x is the first version of the HTTP protocol used to exchange information on the World Wide Web. It was introduced in 1991 and has two major revisions: HTTP/1.0 and HTTP/1.1. HTTP/1.x has some limitations, such as:
- Text-based framing: HTTP/1.x uses plain text to format messages, which can cause parsing errors and overhead.
- No header compression: HTTP/1.x does not compress HTTP header fields, which can increase bandwidth usage and latency.
- No multiplexing: HTTP/1.x allows only one request and response per TCP connection, which can cause head-of-line blocking and poor resource utilization.
- No server push: HTTP/1.x does not enable servers to send resources to clients before they are requested, which can affect page load speed and user experience.
- No stream prioritization: HTTP/1.x does not allow clients and servers to assign priorities to different streams of data, which can affect resource delivery and network performance.
HTTP/1.x is compatible with HTTP semantics, such as methods, status codes, URIs, and header fields. However, it is less efficient and secure than newer versions of HTTP. HTTP/1.0 is the default version used in HTTP if there is no Connection header, or if its value is set to close. HTTP/1.1 is the default version used in HTTP unless otherwise specified by the Connection header.
HTTP/2 is the second version of the HTTP protocol used to exchange information on the World Wide Web. It was derived from the experimental SPDY protocol developed by Google. HTTP/2 was standardized by the Internet Engineering Task Force (IETF) in 2015. HTTP/2 introduces several improvements over HTTP/1.1, such as:
- Binary framing: HTTP/2 uses binary encoding instead of plain text to format messages, which reduces parsing errors and overhead.
- Header compression: HTTP/2 compresses HTTP header fields using a new algorithm called HPACK, which reduces bandwidth usage and latency.
- Multiplexing: HTTP/2 allows multiple requests and responses to be sent over a single TCP connection, which eliminates head-of-line blocking and improves resource utilization.
- Server push: HTTP/2 enables servers to send resources to clients before they are requested, which can improve page load speed and user experience.
- Stream prioritization: HTTP/2 allows clients and servers to assign priorities to different streams of data, which can optimize resource delivery and network performance.
HTTP/2 is compatible with HTTP/1.1 semantics, such as methods, status codes, URIs, and header fields. However, it changes how the data is framed and transported between the client and the server. HTTP/2 is supported by most major browsers and servers.
HTTP/3 is the third major version of the Hypertext Transfer Protocol used to exchange information on the World Wide Web. It is based on a new transport protocol called QUIC (Quick UDP Internet Connections) that uses UDP instead of TCP. HTTP/3 aims to improve the performance, reliability, and security of data transmission over the Internet by introducing features such as:
- Faster connection establishment: QUIC allows TLS version negotiation to happen at the same time as the cryptographic and transport handshakes.
- Zero round-trip time (0-RTT): For servers they have already connected to, clients can skip the handshake requirement and send data immediately.
- More comprehensive encryption: QUIC provides encryption by default and protects against various attacks on the transport layer.
- Multiplexing and stream prioritization: QUIC supports multiple streams of data within a single connection and allows clients and servers to assign priorities to different streams.
- Congestion control and recovery: QUIC adapts to changing network conditions and recovers from packet loss without blocking all streams of data.
HTTP/3 is still under development and not widely supported by browsers or servers yet.