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Modern Protocol Testing

ZSTD Compression Test

Check if any website supports modern RFC 8878 Zstandard (zstd) compression. Benchmark payload sizes against Brotli and Gzip to measure real-world bandwidth and throughput gains.

  • RFC 8878 Zstandard detection
  • 4-way comparison: ZSTD vs Brotli vs Gzip
  • Real-time throughput metrics

Modern Protocol Testing

Benchmark next-generation Zstandard compression

Practical context to help you turn the output into faster, more reliable experiences.
01

Zstandard: The next evolution of web compression

Standardized in RFC 8878, Zstandard (zstd) was created by Yann Collet at Meta to provide both high compression ratios and blazing real-time speeds. Adopted natively by Chrome 123+ and Firefox 126+, ZSTD is rapidly becoming the compression standard of choice for dynamic web assets and API payloads.

While Brotli was tailored for static text, ZSTD achieves competitive file sizes while compressing and decompressing significantly faster, drastically reducing server CPU load during dynamic page generation.

02

Why client decompression throughput matters

Network transmission time is only half of the performance story — once downloaded, the browser must decompress the payload before the JavaScript engine or CSS parser can execute it. On low-to-mid-tier mobile devices, decompression can consume noticeable CPU cycles and delay the main thread.

Zstandard decompresses at several gigabytes per second, unblocking the browser rendering pipeline much faster than legacy algorithms and improving Interaction to Next Paint (INP). Use this tool to verify whether your CDN or origin delivers content-encoding: zstd.

Frequently Asked Questions

Q. What is Zstandard (zstd) compression and how does it compare to Brotli and Gzip?

Zstandard (ZSTD, RFC 8878) is a modern real-time compression algorithm developed by Yann Collet at Meta. While Brotli achieves slightly higher maximum compression ratios for static text, ZSTD achieves comparable compression ratios with 3x to 5x faster decompression speeds and much lower CPU overhead during real-time compression.

Q. Which web browsers support ZSTD compression?

Chrome 123+, Edge 123+, and Firefox 126+ natively support Zstandard compression over HTTPS. When visiting a website, supporting browsers advertise it by including "zstd" in their "Accept-Encoding: zstd, br, gzip" HTTP request header.

Q. Why does decompression speed matter for web performance?

On mobile devices and low-power CPUs, decompressing large JavaScript bundles and complex CSS can cause CPU spikes and block the main browser thread. Because Zstandard decompresses at several gigabytes per second per CPU core, it significantly reduces client-side CPU bottlenecks and improves Interaction to Next Paint (INP) and Time to Interactive (TTI).

Q. How do I enable ZSTD on my web server or CDN?

On Cloudflare, Zstandard compression can be enabled under Speed / Optimization settings for compatible plans. On the modern Caddy web server, simply add "encode zstd gzip br" to your Caddyfile. On Nginx, install the third-party nginx-zstd module.

Q. How does a web server decide whether to serve ZSTD, Brotli, or Gzip?

Modern servers and CDNs prioritize encodings based on the order of algorithms listed in the client’s "Accept-Encoding" request header or server-side priority rules. Browsers that support ZSTD send "zstd, br, gzip", allowing servers to deliver ZSTD when available and seamlessly fall back to Brotli or Gzip for older clients.