<--- Notes

How modern websites work

4 common parts of modern-day websites.


  • Modern websites use JavaScript.

  • Browsers run the javascript using “just-in-time” compilers. These compilers turn developer-friendly JS code into computer-friendly machine code.

  • However, JavaScript had evolved over the years, and not every browser is up-to-date with the latest syntax changes, especially when JavaScript added a bunch of features in 2015 and transitioned from version ES5 to ES6/ES2016.

  • Transpilers/Compilers, like Babel or the fast Rust-written SWC, transpile modern JS code into older JS code.

  • NextJS uses the SWC compiler. They compile the code when you test it and build your project for production.


  • “Minification is the process of removing unnecessary code formatting and comments without changing the code’s functionality. " (source: NextJS)

  • NextJS uses the SWC minifier.


  • Modern web apps break their code across multiple files and import/export things.

  • Bundling is grouping these separate chunks of code into one file.

  • There are a bunch of options: esbuild, rollup, webpack, SWC (swcpack), and turbopack.

  • As of NextJS version 13, they’re using Rust-written turbopack. Prior they used webpack.

Code Splitting

  • Developers split webpage code across different files. Different files import similar and different things from one another.

  • Bundlers bundles code for files that have similar imports, reducing the total number of bundles and redundant code that users would have to load.


  • Compiling is taking developer-friendly code in one language (Javascript) and outputting it in a computer-friendly format, one that browsers understand.

  • NextJS does compiling while you develop and test your code and when you build it for production. (source)

  • NextJS has its compiler (SWC) written in Rust


  • Rendering is showing the user the UI, the HTML styled w/CSS.

  • Dynamic websites use JavaScript to make the UI interactive and render different things.

  • The UI can be pre-rendered or client-side rendered.

  • Pre-rendering can be done by a call to a server that returns the HTML, or by using getStaticProps in NextJS which gets all the things the webpage needs at build time so that NextJS can include the UI in the bundles.

  • Client-side rendering is rendering on the fly, meaning users have to wait for the javascript to run and fill the webpage with HTML.