Comparison
Code splittingvsHTTP multiplexing
Code splitting
the settings screen's code is not downloaded until someone actually opens the settings screen.
Cutting the bundle so that code is only fetched when it is needed, usually along route or interaction boundaries. It is the highest-leverage size optimisation available because it removes code from the initial load without deleting anything. The cost is a request at the moment of use, so a split at the wrong boundary trades a slow first load for a stutter on every click.
Full entry →HTTP multiplexing
you stopped concatenating every file into one, because the connection now carries dozens of requests at once.
Sending many requests concurrently over a single connection, which removed the six-connection limit that made request count so expensive under HTTP/1.1. It is why sprite sheets and domain sharding became obsolete, and why splitting a bundle into more chunks is now cheap. It does not make requests free: each still has a priority, and TCP-level head-of-line blocking on a lossy connection still stalls the whole stream until HTTP/3.
Full entry →