Remember talking to Mike Belshe (SPDY, and H2 spec co-author) before H2 was standardised and even then they were trying to get it dropped from H2 as the benefit

Remember talking to Mike Belshe (SPDY, and H2 spec co-author) before H2 was standardised and even then they were trying to get it dropped from H2 as the benefits were hard to realise, there were plenty of issues and foot guns too One of the largest issues was 'over-pushing' through either sending something that was already in the browser cache, or just trying to push way too much non-critical content (I've seen some truly bad cases of push actually making the page slower to load) There were some proposals to allow the browser to communicate to the server what was already in the local cache but these ran into some issue HTTP Early Hints and Resource Hints have largely removed the need for H2 Push in a way that's much easier to implement, avoids unnecessary fetches and it's easier to reason about too