Libraries compared:

• CSS modules (baseline)
• linaria
• styled-components

About the setup:

• This is a Next.js SSR repository with three URLs - one for linaria (/linaria), one for styled components (/styled-components) and one for the css modules (/regularcss).
• All the URLs load the same component - containing 22 buttons that change their color every 1 second as the React component is rerendered (via state change).
• The styling CSS for these URLs is setup to be generated on the SSR and set internal via <style> tag within the page's HTML.
• The URLs are:
  • /linaria - the page's styling is handled via linaria.
  • /styled-components - the page's styling is handled via styled components.
  • /regularcss - CSS modules.

Page Loading Performance:

• The page loading test was done via WPT (Fast 3G - Virginia, US - Emulated Moto G4):
  • CSS Modules
  • Styled Components Run Results
  • Linaria Run Results
• The start render and the LCP for all the three URLs were similar (no notable deviation).
• The amount of JavaScript loaded for the three routes (sizes in gzipped kBytes):
  • CSS modules : 70.3 kB
  • linaria : 72.4 kB
  • styled-components : 84.1 kB

Re-rendering Performance:

• The rerendering performance was measured by loading the page on Xiaomi Mi A2 mobile (on Chrome 94.0.4 measured via Remote Debugging devtools - Performance tab).
• The library versions for this run were - linaria 3.0, styled components 5.3.3
• The runs were undertaken 5 times and below are the median numbers:

Relavent reading material:

• styled-components/styled-components#2377
• CSS variables performance : https://lisilinhart.info/posts/css-variables-performance/