A while ago we removed FetchEvent.isReload in favor of Request.cache, reasoning that cache mode can tell you whether a navigation is a reload and also back/forward etc.

However it's quite complicated how to map Request.cache to navigation type. Even implementors don't really understand it and it's inconsistent across browsers. See whatwg/fetch#524

Developers want to simply know if a navigation was due to reload or back/forward (see whatwg/fetch#524 (comment)). The proposal is to add something like FetchEvent.navigationLoadType. It could be consistent with window.performance.navigation.type, i.e., four types: 'navigate', 'reload', 'back_forward', and 'undefined'. But we may possibly want to differentiate back vs forward navigation.