NGINX HTTP/3—Configurations, Troubleshooting, and Best Practices

HTTP/3, the latest version of the Hypertext Transfer Protocol, improves upon its predecessors by utilizing QUIC, a transport layer network protocol based on UDP. This shift addresses core issues like connection reliability, latency, and security inherent in HTTP/2 and HTTP/1.x. 

NGINX, a popular web server and reverse proxy, offers HTTP/3 support through its ngx_http_v3_module. Although an experimental feature at the time of writing, this integration is a significant step in web technology advancement. It aims to combine NGINX's performance and versatility with HTTP/3's advanced features.

This article explores NGINX HTTP/3 configurations, best practices, and troubleshooting tips.

Summary of key NGINX HTTP/3 concepts

Concept Description
HTTP/3 HTTP/3 is the third and latest version of the Hypertext Transfer Protocol. It aims to reduce latency by enabling multiplexed connections and improving security and reliability over its predecessors.
QUIC Quick UDP Internet Connections(QUIC) is the transport layer protocol that HTTP/3 uses. It is based on UDP instead of TCP.
NGINX TNGINX is an open-source web server that functions as a reverse proxy, load balancer, mail proxy, and HTTP cache. It is known for its rich feature set, simple configuration, and low resource consumption.

NGINX HTTP/3 introduction

The history of HTTP began as a simple protocol for transferring hypertext documents over the Internet, evolving through versions HTTP/1.0 to HTTP/2. However, these versions faced challenges such as head-of-line blocking (explained in Chapter 1) and latency due to their reliance on TCP. 

HTTP/3, the latest version, aims to overcome these limitations by adopting QUIC (Quick UDP Internet Connections), which uses UDP to reduce connection establishment time and improve congestion control. It allows for multiplexed streams without head-of-line blocking, setting a new standard for web communications.

HTTP/3 works QUIC(UDP) instead of TCP

NGINX is a web server created by Igor Sysoev in 2004 to solve the C10k problem—the challenge of handling ten thousand concurrent connections on a single server. It was designed to use an asynchronous, event-driven approach to managing requests, distinguishing it from the process or thread-based connection handling in traditional web servers like Apache. 

Initially developed as a web server to serve static content efficiently, NGINX has since evolved for everything from load balancer/reverse proxy to API gateway and content caching.

NGINX's supports HTTP/3 through the ngx_http_v3_module.


Deploying HTTP/3 on NGINX

To deploy HTTP/3 on NGINX, compile it with the --with-http_v3_module configuration parameter. Additionally, you must configure your network infrastructure to allow UDP traffic over the standard HTTP/3 port, 443. Please note that QUIC support in NGINX is experimental and should be used cautiously in production environments. 

Check NGINX version

First, check your NGINX version. Support for QUIC and HTTP/3 has only been available since 1.25.0.

nginx -v

You should see output similar to this:

nginx version: nginx/1.25.0
built with OpenSSL 3.0.2 15 Mar 2022
TLS SNI support enabled
configure arguments: --with-cc-opt='-g -O2 -ffile-prefix-map=/build/nginx-YgM00t/nginx-1.24.0=. -flto=auto -ffat-lto-objects -flto=auto -ffat-lto-objects -fstack-protector-strong -Wformat -Werror=format-security -fPIC -flto -ffat-lto-objects -Wdate-time -D_FORTIFY_SOURCE=2' --with-ld-opt='-Wl,-Bsymbolic-functions -flto=auto -ffat-lto-objects -flto=auto -Wl,-z,relro -fPIC -flto -ffat-lto-objects' --prefix=/usr/share/nginx --conf-path=/etc/nginx/nginx.conf --http-log-path=/var/log/nginx/access.log --error-log-path=/var/log/nginx/error.log
--lock-path=/var/lock/nginx.lock --pid-path=/run/nginx.pid
--with-http_v3_module --http-client-body-temp-path=/var/lib/nginx/body --http-fastcgi-temp-path=/var/lib/nginx/fastcgi --http-proxy-temp-path=/var/lib/nginx/proxy --http-scgi-temp-path=/var/lib/nginx/scgi

Optionally, you can also try:

nginx -V 2>&1 | grep -o with-http_v3_module

If you see with-http_v3_module in the output, your NGINX supports HTTP/3.

Build NGINX with required modules

Download a version compatible with HTTP/3 and the QUIC patch from the official repository if needed. 1.25.3 is the latest version as of the time of writing this. You can replace the below with the latest version currently available for you.

wget http://nginx.org/download/nginx-1.25.3.tar.gz
tar -zxvf nginx-1.25.3.tar.gz
cd nginx-1.25.3

Compile NGINX with HTTP/3 Support

A basic configuration command might look like this:

./configure \
    --prefix=/etc/nginx \
    --with-http_ssl_module \
    --with-http_v2_module \
    --with-http_v3_module \
    --with-openssl=$QUICHE_DIR/deps/boringssl \

Adjust the --prefix and other options according to your requirements.

When configuring nginx, it is possible to enable QUIC and HTTP/3 using the --with-http_v3_module configuration parameter. 

To build nginx, it is recommended that an SSL library that provides QUIC support, such as BoringSSL, LibreSSL, or QuicTLS, be used. Otherwise, the OpenSSL compatibility layer will be used, which does not support early data.

Use the following command to configure nginx with BoringSSL:


Alternatively, NGINX can be configured with QuicTLS:


Alternatively, NGINX can be configured with a modern version of LibreSSL:


After configuring, compile and install NGINX:

sudo make install

After installation, you can verify HTTP/3 support by starting NGINX and checking its configuration or using tools that detect HTTP/3 support.

/path/to/nginx -V

Confirm --with-http_v3_module is contained in the output.

Enable HTTP/3 in NGINX server block

An NGINX server block is a configuration unit within the NGINX web server that contains specific directives to define how to respond to requests for a particular domain or subdomain. Server blocks enable NGINX to process requests differently based on various request parameters. 

Below, we give a basic example of server block configuration for HTTP/3.

server {
    # Listen on standard HTTP/2 and HTTPS ports
    listen 443 ssl http2;
    listen [::]:443 ssl http2;

    # Listen on UDP for QUIC+HTTP/3
    listen 443 quic reuseport;
    listen [::]:443 quic reuseport;

    # Specify the key and certificate files
    ssl_certificate /path/to/your/fullchain.pem;
    ssl_certificate_key /path/to/your/privkey.pem;

    # Specify the protocols including QUIC and HTTP/3
    ssl_protocols TLSv1.3;
    ssl_prefer_server_ciphers on;

    # Add Alt-Svc header to advertise HTTP/3 support to clients
    add_header Alt-Svc 'h3-23=":443"'; # Note: 'h3-23' denotes the draft version and may change

    # Server root, index files, server name and other configurations
    root /var/www/html;
    index index.html index.htm;
    server_name example.com;


QUIC-specific security settings

Configuring security for NGINX is crucial for data integrity and trust. To optimize for QUIC and HTTP/3, use OpenSSL 1.1.1 or later for TLS 1.3 support. You should also specify ssl_protocols and ssl_ciphers tailored for optimal performance and compatibility with HTTP/3.

# SSL optimizations for QUIC
ssl_protocols TLSv1.3; # Ensure only TLS 1.3 is used
ssl_ciphers [your-preferred-ciphers-for-TLS1.3];

Advanced Configuration

For more advanced setups, especially in high-traffic environments, consider tuning additional parameters like ssl_session_cache, ssl_session_tickets, and ssl_session_timeout to optimize TLS handshake times and overall server performance. We give an example below.

server {
    listen 443 ssl http2 default_server;
    listen [::]:443 ssl http2 default_server;
    listen 443 quic reuseport default_server;
    listen [::]:443 quic reuseport default_server;

    ssl_certificate /path/to/signed_cert_plus_intermediates;
    ssl_certificate_key /path/to/private_key;
    ssl_session_timeout 1d;
    ssl_session_cache shared:MozSSL:10m;  # about 40000 sessions
    ssl_session_tickets off;

    # curl https://ssl-config.mozilla.org/ffdhe2048.txt > /path/to/dhparam
    ssl_dhparam /path/to/dhparam;

    # intermediate configuration
    ssl_protocols TLSv1.2 TLSv1.3;
    ssl_prefer_server_ciphers off;

    # Enable QUIC and HTTP/3
    ssl_quic on;
    ssl_early_data on;
    add_header Alt-Svc 'h3=":$server_port"; ma=86400';

    # HSTS (ngx_http_headers_module is required) (63072000 seconds)
    add_header Strict-Transport-Security "max-age=63072000" always;

    # OCSP stapling
    ssl_stapling on;
    ssl_stapling_verify on;

    # verify chain of trust of OCSP response using Root CA and Intermediate certs
    ssl_trusted_certificate /path/to/root_CA_cert_plus_intermediates;

    # replace with the IP address of your resolver

Remember, the above configurations are a starting point. Monitoring and adjusting configurations based on performance data is crucial. Identifying bottlenecks and understanding how different settings impact user experience across various global locations are critical to a successful deployment.


Troubleshooting tips for NGINX HTTP/3 

If you run into configuration issues, consider the following.

Debug SSL/TLS misconfiguration

Tools like OpenSSL can help you inspect SSL certificates and test the SSL handshake.

openssl x509 -in /path/to/cert.pem -text -noout

This command displays the details of your certificate to verify its validity.

openssl s_client -connect yourserver.com:443 -alpn h3-29

Replace h3-29 with the appropriate HTTP/3 version supported by your server. This tests the SSL handshake and shows if HTTP/3 negotiation occurs.

Debug QUIC protocol issues

If you're developing or debugging applications using QUIC, quic-go (a QUIC implementation in Go) provides logging capabilities to trace QUIC protocol operations. You can also use tools like Wireshark to capture and analyze QUIC traffic. For a quick command-line check, you can use tcpdump.

sudo tcpdump -i any -U -w quic_traffic.pcap 'udp port 443'

This captures UDP traffic on port 443 and saves it to a file for later analysis. Remember, decrypting QUIC traffic requires the SSL/TLS keys because of QUIC's built-in encryption.

Review NGINX logs

Always check NGINX's error logs for clues on what might be going wrong. They can often point you directly to the source of the problem.

tail -f /var/log/nginx/error.log

Remember, when modifying NGINX configurations or firewall rules, make incremental changes and test each step to isolate the cause of any issues.

Another consideration is the relatively new state of HTTP/3 support across clients and networks; while major browsers support it, not all do by default. Some enterprise networks may not yet be optimized for UDP traffic associated with QUIC.

Best practices for NGINX HTTP/3 configurations

Best practices for deploying NGINX with HTTP/3 are given below.

Include TLS 1.3 in configurations

Include enabling TLS 1.3, as QUIC requires. Make sure these lines appear in your config - as shown in the example above:

# Enable QUIC and HTTP/3
    http3 on;
    ssl_early_data on;
    add_header Alt-Svc 'h3=":$server_port"; ma=86400';

Additional configuration options can be found in the official documentation for NGINX. 

Check firewall and network configuration

Ensure your firewall allows UDP traffic on port 443. You can use iptables or ufw on Linux to check and modify firewall rules.

sudo iptables -L -v -n

Example with ufw.

sudo ufw status

Look for firewall rules allowing or blocking UDP traffic on port 443, and adjust accordingly. Ensure there's an allow rule for 443/udp.

Implement phased rollouts

Test your HTTP/3 setup in a staging environment before rolling it to production. This allows you to identify and resolve any compatibility or performance issues. 

Additionally, the impact on SEO and user analytics should be considered, as the shift to HTTP/3 may affect metrics collection and analysis. To mitigate potential issues, employ a phased rollout and monitor performance and user feedback closely.

It's also important to stay abreast of NGINX news and updates, as improvements and patches related to HTTP/3 are continually being released. 


​​Performance optimization

Performance optimization for HTTP/3 on NGINX focuses on minimizing latency and maximizing throughput. This can involve tuning the underlying UDP settings for QUIC, adjusting session reuse parameters, and optimizing TLS configuration to reduce handshake times. Monitoring and changing settings based on real-world usage patterns are crucial, as the optimal configuration can vary significantly depending on specific traffic loads, content types, and network conditions.

In this context, the Catchpoint platform can support your network monitoring efforts. It provides deep visibility into every aspect of the Internet that impacts your business and revenue. It is like application performance monitoring, but not for your app stack—for your Internet Stack. With over 40 out-of-the-box monitors and the world’s largest global observability network, you can test and monitor all your Internet Stack components, including backbone, wireless, last-mile nodes, and cloud nodes.

Catchpoint also provides real user monitoring to track users' actions while engaging with a website or application. It provides accurate data and metrics to better understand user behavior and insight into a system or service's performance. With Catchpoint's support, businesses can ensure that their transition to HTTP/3 enhances performance and security and aligns with the best user experience outcomes.

Final thoughts

NGINX support for HTTP/3 is indicative of the coming era in global Internet operations. It allows users to take advantage of HTTP/3's benefits, including reduced latency, improved security, and better handling of multiple data streams. 

However, given the early stages of adoption, ensure you test your changes thoroughly before deploying to production. Monitoring network usage will allow you to optimize your application's configuration changes.