Fast: Yarn caches every package it has downloaded, so it never needs to download the same package again. It also does almost everything concurrently to maximize resource utilization. This means even faster installs. Reliable: Using a detailed but concise lockfile format and a deterministic algorithm for install operations, Yarn is able to guarantee that any installation that works on one system will work exactly the same on another system. Secure: Yarn uses checksums to verify the integrity of every installed package before its code is executed