# Seeking Clarification on HTTP/3 Performance Differences Between NGINX 1.27.5 and 1.27.4 **URL:** \ **Category:** NGINX\ **Tags:** performance, quic, http3\ **Created:** [July 11, 2025, 9:57am UTC](https://community.nginx.org/t/seeking-clarification-on-http-3-performance-differences-between-nginx-1-27-5-and-1-27-4/5417 "2025-07-11T09:57:31Z")\ **Posts on this page:** 1\ **Showing post:** 4
**Author:** ![villa](https://avatars.discourse-cdn.com/v4/letter/v/bc79bd/32.png) [@villa](https://community.nginx.org/u/villa)\ **Post date:** [August 5, 2025, 6:11am UTC](https://community.nginx.org/t/seeking-clarification-on-http-3-performance-differences-between-nginx-1-27-5-and-1-27-4/5417/4 "2025-08-05T06:11:32Z")
# Performance Regression Observed in NGINX HTTP/3 After Switching to QUIC Cubic Congestion Control? We conducted HTTP/3 performance tests across NGINX versions 1.25.5, 1.27.4, 1.27.5, 1.28.0, and 1.29.0 under consistent network emulation conditions shown above. Starting from version 1.27.5, NGINX switched its QUIC congestion control algorithm from **reno** to **cubic**. Interestingly, we observed a significant drop in performance in versions using cubic, especially under packet loss conditions. While we are unsure whether this is a coincidence or the root cause, we suggest that future NGINX releases provide a configuration parameter allowing users to select the QUIC congestion control algorithm based on their deployment needs. ## Test Results | Version | No Packet Loss (sec) | 1% Packet Loss (sec) | | --- | --- | --- | | nginx-1.25.5 | 12.329 | 21.339 | | nginx-1.27.4 | 13.592 | 24.173 | | nginx-1.27.5 | 27.251 | 221.720 | | nginx-1.28.0 | 19.456 | 195.452 | | nginx-1.29.0 | 19.498 | 186.282 | --- _[View the full topic](https://community.nginx.org/t/seeking-clarification-on-http-3-performance-differences-between-nginx-1-27-5-and-1-27-4/5417)._