Frontend Performance Checklist For 2025 - Crystallize.com

- **Avoid ** **`@import`** ** in CSS:** The `@import` rule in CSS creates additional HTTP requests and is render-blocking. Each imported file is fetched sequentially, which delays the overall CSS parsing. Instead of `@import`, use `<link rel="stylesheet">` tags in HTML (which can load in parallel) or better yet, combine CSS files at build time when possible., … - **Use HTTPS (TLS):** This is non-negotiable today. Apart from security, modern HTTPS is faster than HTTP in many cases. Every modern browser also **flags non-HTTPS sites as insecure** and may even limit their features. Moreover, Google uses HTTPS as a **ranking signal** for SEO. So, enable HTTPS and HTTP/2+ (most hosting platforms have this by default now). - **Minimize total HTTP requests:** In the past, combining files to reduce requests was crucial due to HTTP/1.x limitations. With HTTP/2+ this is less of an issue, since multiple files can load in parallel over one connection. However, each script or resource still has overhead, and numerous requests can add up on high-latency connections. Audit the number of resources your pages load. Remove any that aren’t necessary (fonts, icons, analytics, etc., that aren’t providing value). - **Use HTTP/2 or HTTP/3:** If your hosting still uses HTTP/1.1, it’s time to upgrade. HTTP/2 brought significant performance improvements, like multiplexing (many resources over one connection) and header compression, which reduce latency. Going a step further, HTTP/3 (QUIC) is now emerging as the next standard – it runs over UDP with encryption and offers even faster connection setup and better resilience to network issues. HTTP/3 can improve page load times, especially on mobile or poor networks, thanks to zero round-trip handshakes and eliminating head-of-line blocking. … - **Maintain a single protocol (no mixed content):** Ensure that all resources are requested via the same protocol as your page (which should be HTTPS). Mixing HTTPS and HTTP can lead to blocking of content or at best a performance hit (and security risk).