To set up a catch-all server block in Nginx, define a server block without a server_name or use an empty string, listen on port 80 (or 443) with default_server, and decide how to handle unmatched traffic. First, understand that a catch-all block catches requests not matching any defined server blocks by using the Host header. Second, create the server block using listen 80 default_server;, server_name "";, and typically return 444; to drop unwanted traffic silently. Third, consider variations like redirecting unknown domains, serving an informational page, or logging suspicious activity. Fourth, if using HTTPS, configure a similar block for port 443 with a certificate. Finally, test your configuration with sudo nginx -t, reload Nginx with sudo systemctl reload nginx, and ensure firewall rules allow traffic to pass through required ports.
Setting up a catch-all server block in Nginx is actually pretty straightforward — it’s just not something most beginners come across right away. The idea is to handle requests that don’t match any of your defined server blocks, which can help avoid unexpected behavior or errors when someone hits your server with an unknown domain.
Here’s how you do it.
What a catch-all server block does
Before diving into the setup, let's quickly clarify what this does. Nginx processes incoming HTTP requests by matching the Host
header against the server_name
directives in your configured server blocks. If none match, it routes the request to the default server block.
A catch-all server block usually listens on port 80 (or 443 for HTTPS) and has no specific server_name
. It acts as a fallback — useful for catching misconfigured DNS entries, preventing unintended access, or even redirecting unknown traffic somewhere safe.
How to create the server block
To set up a catch-all block, you’ll need to define a server in Nginx that doesn't specify a server_name
, or explicitly uses an empty string (""
). Here's a minimal example:
server { listen 80 default_server; server_name ""; return 444; }
Let’s break that down:
listen 80 default_server;
tells Nginx this block should be used when no other server matches.server_name "";
ensures it catches anything without a match.return 444;
closes the connection silently (a common practice for unwanted traffic).
You can also log these requests if you're curious about what’s hitting your server unexpectedly.
Common use cases and variations
There are a few reasons you might want a catch-all block beyond just dropping traffic:
Redirect unknown domains to a main site
return https://yourmaindomain.com$request_uri;
Serve a simple informational page
Useful if you’re troubleshooting or managing multiple domains.Log suspicious activity
You can set up a separate access log to monitor what kind of traffic ends up here.
If you have SSL enabled, you can do the same for port 443, but keep in mind you’ll need a certificate. A self-signed cert works fine since no one should be visiting this block anyway.
Don’t forget to test and reload
After updating your Nginx config, always test it before reloading:
sudo nginx -t
If everything looks good, apply the changes:
sudo systemctl reload nginx
It’s easy to accidentally leave a typo in your config file, so this step is worth taking seriously. Also, make sure your firewall allows traffic on port 80 (and 443 if needed), otherwise your real sites won’t get traffic while the catch-all sits idle.
That’s basically it. Not flashy, but super useful once you understand how Nginx matches server names. Just make sure your default block doesn’t accidentally expose something you didn’t intend.
The above is the detailed content of How to set up a catch-all server block?. For more information, please follow other related articles on the PHP Chinese website!

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