Performance work that starts after the design is signed off is damage limitation. The expensive decisions — a full-bleed video, a webfont family, a hero that cannot render until data arrives — are made long before anyone opens a profiler.
Budget before layout
Agree what the first screen is allowed to cost, in kilobytes and in seconds, while the layout is still a sketch. A budget set afterwards is a wish.
The things that actually move
- Media: dimensions, format, and whether it blocks first paint at all
- Fonts: how many families, how many weights, and what shows while they load
- Layout stability: reserved space for anything that arrives late
- JavaScript: what runs before the page is usable
Measure the thing the visitor feels
A build that compiles quickly and a page that feels quick are different achievements. Test on a mid-range phone on a throttled connection, because that is the visitor most likely to leave.
A successful build is not a successful page.