Postmortem: How a Tailwind CSS 3.4 Purge Bug Caused Our Next.js 15 App to Have 2MB of Unused CSS

In Q1 2024, a production Next.js 15 e-commerce app we audited shipped with 2.14MB of unused CSS, traced directly to a subtle interaction between Tailwind CSS 3.4’s purge logic and Next.js 15’s App Router static generation. That’s 68% of the total CSS...