Difference Between HTTP/1.1 And HTTP/2
These are the high-level differences between HTTP1 and HTTP2:
- HTTP2 is binary, instead of textual
- HTTP2 is fully multiplexed, instead of ordered and blocking
- HTTP2 can, therefore, use one connection for parallelism
- HTP2 uses header compression to reduce overhead
- HTTP2 allows servers to “push” responses proactively into client caches
Multiplexing: HTTP/1.1 loads resources one after the other, so if one resource cannot be loaded, it blocks all the other resources behind it. In contrast, HTTP/2 is able to use a single TCP connection to send multiple streams of data at once so that no one resource blocks any other resource. HTTP/2 does this by splitting data into binary-code messages and numbering these messages so that the client knows which stream each binary message belongs to.
Server push: Typically, a server only serves content to a client device if the client asks for it. However, this approach is not always practical for modern webpages, which often involve several dozen separate resources that the client must request. HTTP/2 solves this problem by allowing a server to “push” content to a client before the client asks for it. The server also sends a message letting the client know what pushed content to expect — like if Bob had sent Alice a Table of Contents of his novel before sending the whole thing.
Header compression: Small files load more quickly than large ones. To speed up web performance, both HTTP/1.1 and HTTP/2 compress HTTP messages to make them smaller. However, HTTP/2 uses a more advanced compression method called HPACK that eliminates redundant information in HTTP header packets. This eliminates a few bytes from every HTTP packet. Given the volume of HTTP packets involved in loading even a single webpage, those bytes add up quickly, resulting in faster loading.
