HTTP - Versions

---

---

This chapter discusses about different versions of HTTP as they have evolved over the years since release of first HTTP version in 1991. This chapter provides a detailed explanation of HTTP versions, their features, use cases and improvements over the years.

Versions of HTTP

Here is a list of different versions of HTTP mentioned below.

• HTTP/0.9
• HTTP/1.0
• HTTP/1.1
• HTTP/2
• HTTP/3

HTTP/0.9

HTTP/0.9 was the first version of HTTP protocol. HTTP/0.9 was very simple protocol with only method as GET method. It was used to retrieve HTML document over the web. In this version of HTTP, there was no HTTP headers and request message consisted of GET method and source path.

Key Features

The key features of HTTP/0.9 is mentioned below.

• It supported a single method i.e GET method.
• No support of HTTP headers.
• The response was very simple, consisted of file itself without metadata.

Use Cases

It was primarily used for basic document retrieval and for lightweight communication where only basic HTML data is required.

HTTP/1.0

The HTTP/1.0 was the updated version of HTTP/0.9, released in 1996. It introduced two new methods i.e POST and HEAD methods, HTTP headers, response status code. It allowed transmission of document, other than plain HTML files.

Key Features

The key features of HTTP/1.0 is mentioned below.

• It introduced new methods i.e POST and HEAD methods.
• It supported HTTP headers for both requests and responses.
• It supported response status codes such as 200 OK and 404 NOT FOUND.
• It offered support for basic caching mechanism using 'Expires' header.
• In HTTP/1.0, new connection is made for every new request and connection is closed after the response is sent back.

Improvements from Previous Version

We have mentioned the improvements in HTTP/1.0 from its previous version.

• Support for methods other than Get method
• Flexible and informative communication through metadata in HTTP headers.
• HTTP protocol was not limited to just retrieving information.

Use Cases

• Basic E-Commerce Websites: For handling simple forms, online transaction, and order placement.
• Initial Multimedia: It allowed limited multimedia delivery capability of images, audio and video files.
• Early API Communication: It is used in early web applications with limited requirements for basic REST-like communication.
• Static and Semi-Dynamic Websites: It is suitable for early websites with minimal interactivity, for example, blogs, news sites, and personal portfolios.

HTTP/1.1

HTTP/1.1 was released in 1999. It introduced many changes after HTTP/1.0 such as persistent connection allowing multiple request and response to be sent over single connection.

HTTP/1.1 also introduced chunk transfer encoding to transfer large or dynamically generated content without knowing content length. New HTTP methods such as OPTIONS, TRACE and PATCH improved caching mechanism along with headers such as Cache-Control and If-Modified-Since.

Key Features

The key features of HTTP/1.1 is mentioned below.

• Persistent Connection: HTTP/1.1 allows to send multiple requests and responses from same TCP connection.
• Chunked Data Transfer: HTTP/1.1 allows servers to send responses in small chunks helping in handling dynamic data.
• Range Requests: HTTP/1.1 allows clients to download specific parts of resource.
• Content Negotiation:HTTP/1.1 allows clients and servers to agree on format and language of the response.
• Security: HTTP/1.1 improved the SSL/TLS support, making the connections more secure.
• Error Codes: For handling specific response situations, HTTP/1.1 introduced additional status codes.

Improvements from Previous Versions

We have mentioned the improvements in HTTP/1.1 from its previous versions.

• In HTTP/1.1, connection can be reused i.e same TCP connection can be reused for multiple requests and responses. It helps in reducing latency.
• The HTTP/1.1 introduced better caching mechanism with Cache-Control header than HTTP/1.0 Expires header.
• The HTTP/1.1 support for virtual hosting overcame the limitation of HTTP/1.0 using mandatory HOST header.
• The HTTP/1.1 allowed to send data in pieces without precomputing its size. It helps in improving real time response delivery.
• The HTTP/1.1 allowed data compression using Content-Encoding reducing the payload size compared to HTTP/1.0.
• It allowed support for sending multiple requests without waiting for response from the server.

Use Cases

• Dynamic Websites: Due to support for persistent connections, it allowed social media platforms and forums to load faster and handle frequent updates more efficiently.
• Enterprise Web Applications: Large scale internal business tools like ERP systems or project management systems make use of persistent connection. It improves performance for tools requiring real-time data updates.
• Search Engines:HTTP/1.1 features such as indexing through persistent connections, pipelining and faster content retrieval improved the efficiency of search engines.
• Caching: Introduction of caching headers such as Cache-Control and Etag allowed Content Delivery Networks (CDNs) to cache static resources such as images, scripts, and stylesheets with faster delivery and reduced server load.

HTTP/2

HTTP/2 was released in 2015. It was a major upgrade after HTTP/1.1. It introduced many new improvements aiming to improve page load times, reduce latency, and improve the efficiency of resource utilization. It introduced multiplexing allowing multiple requests and responses to be sent simultaneously over a single connection. HTTP/2 also implemented header compression using HPACK, and added features like server push, to send resources to clients before they are requested.

Key Features

The key features of HTTP/2 is mentioned below.

• Multiplexing: HTTP/2 allows to send multiple requests and responses simultaneously over a single connection.
• Header Compression: HTTP/2 uses header compression algorithm 'HPACK' to compress the headers, which helps in reducing size and improving performance.
• Stream Prioritization: HTTP/2 prioritizes critical resources to deliver faster.
• Server Push: Server proactively sends resources to clients if it predicts that client will need the resources.
• Better Security: HTTP/2 make use of TLS and uses encryption to improve the security.

Improvements from Previous Version

We have mentioned the improvements in HTTP/2 from its previous versions.

• HTTP/2 allows multiplexing, that allows parallel requests and responses over a single connection unlike HTTP/1.1 that processed requests sequentially.
• HTTP/2 compresses headers using HPACK. It reduces the request and response header size improving the performance unlike HTTP that used to send full headers.
• HTTP/2 prioritize critical resource to load faster which was not present in previous version of HTTP.
• If the server predicts that client will need any resource then server automatically sends the resource to client in HTTP/2.
• HTTP/2 features such as connection reuse, header compression, and reduced latency makes it more efficient for mobile devices and for slower networks.

Use Cases

• Modern Web Applications: HTTP/2 is ideal for web apps requiring multiple API calls and for single page applications as multiplexing helps in sending and receiving multiple requests and responses simultaneously.
• Real-Time Communication: Apps such as chat system, live notification and collaborative tools make use of connection reuse and multiplexing for low latency and fast data exchange.
• Video Streaming Platforms: HTTP/2 features such as chunked data transfer, multiplexing, and server push helps these platforms in smooth video playback and minimizing the buffering time and interruptions.
• CDN: HTTP/2 features such as improved caching, header compression, and multiplexing helps CDN to deliver web content faster.

HTTP/3

HTTP/3 was released in 2022 which replaced TCP with QUIC protocol as its transport layer. QUIC is based on UDP protocol that improves reliability of connection and performance using multiplexing, stream independence, and built-in encryption for security.

Key Features

The key features of HTTP/3 is mentioned below.

• QUIC Protocol: HTTP/3 uses QUIC protocol based on UDP protocol which is faster and more reliable than TCP protocol used by HTTP/2.
• Stream Independence: HTTP/3 treats each stream independently, eliminating head-of-line(HOL) blocking so that one delayed stream does not affect others.
• Enhanced Security: QUIC protocol is integrated with security making encryption mandatory for all connection.
• Compatibility: HTTP/3 can coexist with its previous versions i.e HTTP/2 and HTTP/1.1.
• Faster Connection: QUIC protocol combines the handshake of transport and encryption in a single step which reduces the connection setup time.

Improvements from Previous Version

We have mentioned the improvements in HTTP/3 from its previous versions.

• HTTP/3 make use of QUIC protocol unlike HTTP/2 which used TCP protocol which makes it faster and efficient protocol than HTTP/2 as there is no head-of-line blocking(delay in processing first item blocks the processing of next item in queue).
• HTTP/3 integrates security natively with QUIC, unlike HTTP/2 which worked alongside TLS.
• HTTP/3 solves the issue of head-of-line blocking by fully isolating streams, improving responsiveness for applications.
• HTTP/3 performs better in mobile and wireless devices than HTTP/2 as it adapts to frequent changes in IP address.
• In HTTP/2, because of it's sequential nature, a packet loss affects all streams but in HTTP/3 only affected stream delays.

Use Cases

• Real-Time Media and Gaming: HTTP/3 performs well where low latency is important such as video streaming, online games and video conferencing.
• Cloud-Native Applications: Cloud native applications make use of low latency and connection stability to scale across cloud environments.
• Mobile-First Applications: QUIC protocol reduces setup time and stable performance even in fluctuations such as switching between Wi-Fi and 4G/5G networks.

Differences Between HTTP Versions

The following table highlights the differences between HTTP/0.9, HTTP/1.0, HTTP/1.1, HTTP/2 and HTTP/3.