HTTP/1 (1996) vs HTTP/2 (2015)

1. HTTP/1 req/res are sent sequentially, one after another. This means that if you have several resources (e.g., photos, stylesheets, scripts) to load for a single web page, each resource requires a separate connection, which can lead to latency and slower page loading times. Where as HTTP/2 introduces request multiplexing, which allows several requests and responses to be delivered and received in simultaneously over a single connection and thus minimising the latency and speeds up the loading of multi-resource web pages.
2. HTTP/1 headers are uncompressed. This can result in significant latency in the form of redundant header data being delivered with each request and response. HTTP/2, on the other hand, employs header compression (HPACK) to minimise the size of headers, hence reducing the amount of data delivered and enhancing efficiency.
3. HTTP/1 does not have built-in capability for prioritising requests. All requests are treated identically, which might lead to poor performance for essential resources. Whereas HTTP/2 supports stream prioritisation. This means that more critical resources can be prioritised, resulting in faster loading and a better user experience.
4. HTTP/1 requires the server to wait until the client requests additional resources before sending them. This can result in inefficiencies because the server may be aware of which resources will be required but must wait for the client to request them. HTTP/2, on the other hand, introduces server push, which allows the server to provide resources to the client that it expects the client will need. This minimises round-trip times and speeds up page loading.
5. I checked couple of websites, some use HTTP/1.1 and most of them use HTTP/2. Also HTTP/3 has been introduced in 2022