Aim to keep the initial HTML and inline critical CSS under roughly 14 KB compressed for a faster first load.
TCP slow start limits how much data a server can send before waiting for acknowledgments. With a 10-segment initial congestion window and 1,460 bytes per segment, the first batch holds 14,600 bytes. Fitting the response into this window can avoid an extra network round-trip.
Keep it small
- Use simple HTML and minimal inline critical CSS.
- Remove unnecessary JavaScript, unused CSS, and third-party scripts.
- Defer nonessential scripts and lazy-load below-the-fold images.
- Enable Brotli or gzip compression and measure the compressed response size.
Not a hard limit
14 KB is a rule of thumb for the initial response, not a requirement for the entire website or a guarantee of maximum download speed. HTTP headers and TLS overhead need room too. Connection setup, server settings, additional asset requests, and browser rendering still affect load time.