What is HTTP/2?

HTTP/2: Major upgrade to web page transfer protocol

HTTP/2 is the latest version of the Hypertext Transfer Protocol (HTTP) designed to replace HTTP/1.1. It significantly improves data transmission efficiency and speed through features such as binary data, compression headers, pipelineization, multiplexing and server push.

Difference between HTTP/2 and HTTP/1.1

HTTP/2 (originally named HTTP/2.0) originated from the SPDY protocol designed by Google in 2009. HTTP/1.1 has some limitations, such as designing in an era of small web page sizes and limited CSS and JavaScript applications, it is difficult to cope with the current situation of high bandwidth, Ajax drivers, single-page applications and client frameworks. The main goal of HTTP/2 is to reduce latency, which improves efficiency through the following technical means:

1. Binary data: HTTP/2 uses binary data, which is more efficient than text data of HTTP/1.1.
2. Compress header: HTTP/2 compresses information (data description, source, type, length, cache time, etc.) to reduce the transmission amount.
3. Piplied: HTTP/1.1 handles requests and responses in sequence, and HTTP/2 is asynchronously processed, giving priority to smaller or faster responses.
4. Multiplexing: HTTP/1.1 can only handle one request per TCP connection, and HTTP/2 allows multiple requests and responses to be processed simultaneously on the same connection.
5. Server push: Server can send resources before the client requests. For example, in HTTP/1.1, the browser needs to download HTML and parse it before loading JavaScript files, while the HTTP/2 server can use it in Push JavaScript files before HTML parsing.

Is HTTP/2 performance improvement significant?

Although the test results vary by system, the comparative test of HTTP/1.1 vs. HTTP/2 (using HTTPS) usually shows that HTTP/2 speed is more than 10 times faster, even in the case of secure connections.

Is HTTP/2 now possible?

Yes. But it can only be enabled if both the web server and browser support HTTP/2, otherwise the connection will fall back to HTTP/1.1. At the end of 2016, about 11% of websites supported HTTP/2. Currently, all mainstream browsers (Firefox, Safari, Edge, Chrome, etc.) support HTTP/2.

You can use the HTTP/2 testing tool provided by keycdn.com to check if your host is enabled. If you are using a managed or shared hosting, you may need to contact the hosting provider to enable HTTP/2. Ideally, it is best to use a host with HTTP/2 enabled by default. When using HTTP/2, it is recommended to use HTTPS because most browsers only support HTTP/2 in encryption.

Does my website need to be updated?

Not required. HTTP/2 is backward compatible with HTTP/1.1. However, some optimization strategies for HTTP/1.1 may actually reduce efficiency in HTTP/2 environments. For example, reducing the number of requests is important for HTTP/1.1, but in HTTP/2, multiple requests are less expensive.

You may be using a build system or manual process to:

• Convert multiple images to single image sprite image
• Inline images in HTML page or CSS file
• Merge and compress CSS and JavaScript into a single file

These methods are effective in HTTP/1.1, but may actually reduce efficiency in HTTP/2.

HTTP/2 FAQ

• What is the main difference between HTTP/1.1 and HTTP/2? HTTP/2 is an upgrade to HTTP/1.1, with major improvements including binary framing, multiplexing, server push and head compression.
• How to improve website performance with HTTP/2? Multiplexing allows multiple requests to be sent simultaneously, reducing latency; header compression reduces data transmission.
• Is HTTP/2 compatible with all browsers and servers? Most modern browsers and servers support HTTP/2, but not all features are compatible.
• How to deal with security issues with HTTP/2? HTTP/2 itself does not provide additional security features, but is usually used with HTTPS to provide secure and encrypted communication.
• What is the server push in HTTP/2? How does it work? Server push allows the server to send resources before the client requests, reducing waiting time.
• How does HTTP/2 handle mobile devices? HTTP/2 is well designed and suitable for mobile devices.
• What is the impact of HTTP/2 on SEO? Faster page loading speeds can improve user experience, which can affect search engine rankings.
• How to implement HTTP/2 on a website? Update the web server software to a version that supports HTTP/2 and configure the server to enable HTTP/2 features.
• Can HTTP/2 and HTTP/1.1 coexist? Yes, HTTP/2 is backward compatible with HTTP/1.1.
• What is the future of HTTP/2? HTTP/2 has been widely used, and its characteristics will become more and more important. HTTP/3 is under development.

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