Web Performance Checklist

What this checklist is

A release checklist for fast websites, organised around the three Core Web Vitals and the guidance on web.dev. Each check says how much it matters and exactly how to confirm it, from field data and server response time to the LCP image, long tasks, layout shifts, fonts, the back/forward cache and monitoring after release.

It has 8 chapters and 35 checks, each with how to verify it and how much it matters. For web developers shipping to production.

Chapter by chapter

1. Measure before you optimise (4 checks)

Know which metric is failing for real users before you change anything. These checks set up field data, lab tools and the right targets.

2. Server response and TTFB (4 checks)

Every millisecond before the first byte delays everything after it. These checks keep the server, redirects and caching from eating the LCP budget.

3. LCP and images (6 checks)

The largest element on screen is usually an image or a heading. These checks get it discovered, fetched and painted as early as possible.

4. JavaScript and INP (6 checks)

Responsiveness is about keeping the main thread free. These checks break up long tasks, slim event handlers and keep rendering cheap.

5. CLS and layout stability (4 checks)

Content that jumps makes people tap the wrong thing. These checks reserve space before content arrives and animate without moving layout.

6. Fonts and CSS (3 checks)

Web fonts and stylesheets block text and cause late reflows. These checks load them early and keep the fallback close to the final look.

7. Caching, delivery and the back/forward cache (5 checks)

Repeat visits and back navigations should be close to instant. These checks cover HTTP caching, compression, code splitting and keeping pages eligible for the back/forward cache.

8. Monitoring and budgets (3 checks)

Performance regresses one small change at a time. These checks make regressions visible before users notice them.

How it works on Sefism

The checklist is one page: each check has a severity (must, should or nice to have) and a concrete way to verify it, and members can tick checks off as they go. The opening chapters are open to everyone. Adding it to your account uses credits, opens every chapter and keeps your progress.

Every claim is checked against the sources listed on the page (8 cited).