Comparison
Server-side renderingvsTime to first byte
Server-side rendering
the HTML arrives with the content already in it, and the page is readable before any script runs.
Running the component code on the server for each request and sending finished HTML. It gets content on screen sooner and gives crawlers something to read, at the cost of a server that must render on every request and a time-to-first-byte that now includes your data fetching. The rendered HTML is inert until hydration, so 'visible' and 'usable' become two different moments you have to measure separately.
Full entry →Time to first byte
the browser sat waiting with an empty tab before a single byte of HTML came back.
The interval from starting the navigation to the first byte of the response, covering redirects, DNS, connection setup and the server's own thinking time. It is the floor under every other loading metric: nothing can paint sooner than this. A slow one is usually a server or origin problem rather than a frontend one, which makes it the first number to check before optimising anything in the browser.
Full entry →