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About The Author

Vitaly Friedman loves beautiful content and doesn’t like to give in easily. When he is not writing, he’s most probably running front-end & UX … More about Vitaly ↬

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Let’s make 2021… fast! An annual front-end performance checklist with everything you need to know to create fast experiences on the web today, from metrics to tooling and front-end techniques. Updated since 2016.

Table of Contents

  1. Getting Ready: Planning And Metrics
  2. Setting Realistic Goals
  3. Defining The Environment
  4. Assets Optimizations
  5. Build Optimizations
  6. Delivery Optimizations
  7. Networking, HTTP/2, HTTP/3
  8. Testing And Monitoring
  9. Quick Wins
  10. Everything on one page
  11. Download The Checklist (PDF, Apple Pages, MS Word)
  12. Everything on one page
  13. Download The Checklist (PDF, Apple Pages, MS Word)
  14. Subscribe to our email newsletter to not miss the next guides.

Quick Wins

This list is quite comprehensive, and completing all of the optimizations might take quite a while. So, if you had just 1 hour to get significant improvements, what would you do? Let’s boil it all down to 17 low-hanging fruits . Obviously, before you start and once you finish, measure results, including Largest Contentful Paint and Time To Interactive on a 3G and cable connection.

  1. Measure the real world experience and set appropriate goals. Aim to be at least 20% faster than your fastest competitor. Stay within Largest Contentful Paint < 2.5s, a First Input Delay < 100ms, Time to Interactive < 5s on slow 3G, for repeat visits, TTI < 2s. Optimize at least for First Contentful Paint and Time To Interactive.
  2. Optimize images with Squoosh , mozjpeg , guetzli , pingo and SVGOMG , and serve AVIF/WebP with an image CDN.
  3. Prepare critical CSS for your main templates, and inline them in the of each template. For CSS/JS, operate within a critical file size budget of max. 170KB gzipped (0.7MB decompressed).
  4. Trim, optimize, defer and lazy-load scripts. Invest in the config of your bundler to remove redundancies and check lightweight alternatives.
  5. Always self-host your static assets and always prefer to self-host third-party assets. Limit the impact of third-party scripts. Use facades, load widgets on interaction and beware of anti-flicker snippets.
  6. Be selective when choosing a framework. For single-page-applications, identify critical pages and serve them statically, or at least prerender them, and use progressive hydration on component-level and import modules on interaction.
  7. Client-side rendering alone isn't a good choice for performance. Prerender if your pages don’t change much, and defer the booting of frameworks if you can. If possible, use streaming server-side rendering.
  8. Serve legacy code only to legacy browsers with