FF mobile: Load pages offline from cache?

Firefox mobile can sometimes load previously visited resources from cache, but it depends on how the website handles caching and whether the required files are still available in the browser cache. Normal HTTP cache is not really designed to make an entire page reliably available offline. If you need reliable offline access, a service worker with the Cache API is usually a better approach. The service worker can cache the HTML, CSS, JavaScript, and other required resources and then serve them when the device is offline. It would also be useful to check Firefox's current mobile behavior around back-forward cache, HTTP caching, and service workers, because those mechanisms work differently.