What's the practical difference between cache-first, network-first, and stale-while-revalidate?

Short interview answer

Cache-first checks the cache and only goes to the network on a miss, favoring speed and offline availability over freshness, appropriate for a static app shell. Network-first tries the network first and falls back to cache on failure, favoring freshness while staying usable offline. Stale-while-revalidate returns the cached response immediately for speed, then fetches in the background to update the cache for next time.