This type of thing usually ends up being “death by a thousand cuts”. async + defer help out, but they do still incur parsing and evaluation (iirc, before document onload event) overhead. If you delay loading until you’re sure the page is interactice, you’ll end up loading third-party pretty late (which impacts metrics, and usually isn’t out of the box supported).
On a standard product-ey site with retargeting ads, user tracking, etc. this third-party slowdown is significant.
All of this is exacerbated on lower-end devices, and non-WiFi Internet.
On a standard product-ey site with retargeting ads, user tracking, etc. this third-party slowdown is significant.
All of this is exacerbated on lower-end devices, and non-WiFi Internet.