Ads as a Performance Budget Problem

Ads are often treated as external integrations, but from the browser's perspective they compete for the same main thread, memory, and network bandwidth as first-party code. Drawing on experience improving the TanStack documentation site, the author argues that ads should be treated as a defined slice of the performance budget rather than an afterthought. This reframes the question from 'how do we add ads without hurting performance?' to 'what portion of our budget do we allocate to monetization, and where do we claw it back elsewhere?' Practical offsets include removing dead JavaScript and CSS, simplifying component boundaries, and delaying non-essential interactivity. The post also highlights why documentation sites are especially sensitive to layout shifts and load delays, and concludes that the real engineering challenge is containment — designing systems that remain stable and fast as they evolve.