HTTP/1.1 is a version of an HTTP networking protocol used for communication over the internet. in HTTP/1.1, one request is sent over one TCP connection to a server. The server processes one request at a time per connection, but connection remains open for subsequent requests after an initial request/response cycle. What does it mean that server is blocked (waiting) for the current request to complete before it can process next one. That means that, if multiple requests are being made at the same time, they are processed one after another and the other ones are pending.
Client Server
[REQUEST]
GET main.js -------->
[RESPONSE]
GET main.js <--------
Modern browser optimise connection by using parallel connections (typically 6) to send multiple requests at once and that helps to improve network throughput. This doesn’t mean that all requests are resolved in parallel, but they are processed serially.
Client Server
[REQUEST]
GET main.js --------->
GET main.css -------->
GET main.html ------->
[RESPONSE]
GET main.js <---------
GET main.css <--------
GET main.html <-------