Page speed Standard Understanding

PageSpeed
- Understanding Lab vs Field Data
  - Lab Data
  - Field Data
- Lighthouse performance scoring Lighthouse performance scoring | Chrome for Developers → Using HTTPArchive
- Lighthouse Scoring Calculator : Lighthouse Scoring calculator
- User-centric performance metrics User-centric performance metrics | Articles | web.dev
Browser Life Cycle DigitalOcean
The critical rendering path Understanding the critical rendering path, rendering pages in 1 second
- DOM
- CSSOM
- Render Tree
- Layout → Paint
- Dealing with Javascript
- Parser blocking vs render blocking
  - If there is any inline <script> under an external CSS's <link> tag, even if that is just an empty <script> tag that contains no JavaScript at all, the DOM construction for the HTML below that <script> tag will still be blocked util the external CSS is fetched. If you have a slow network connection, that empty <script> still causes a long delay of DOM construction. Because the <script> tag waits for the external CSS, and DOM construction waits for the script. In this case the external CSS resource implicitly causes a parser-blocking.
- Make sure no critical requests are redirected.