What you need to know
Third-party code can add network requests, block the main thread, and create privacy obligations. A small widget may slow every route even when most visitors do not use it.
How to apply it
List each script's purpose and owner, delay non-essential work until after the page is usable, load widgets only where needed, and remove scripts without a clear benefit.
Common mistake to avoid
Do not load duplicate tracking tags or rely on an external script for a core navigation feature. Have a plan if the vendor is slow or unavailable.