Rack proxy server for development

This is an (almost) complete rewrite of Prax in Crystal, a Ruby-inspired language that compiles down to LLVM. This version should avoid problems with version managers, since Prax is now a binary application that don't rely on Ruby anymore (except for Rack and rackup).

Please refer to the wiki for more information:


You can download a Debian / Ubuntu package for 64bits kernel on the releases page. For other systems, you'll have to follow the Manual Install Guide.

How it works

  1. resolves *.test and *.localhost domains to and ::1 (localhost);
  2. redirects the :80 and :443 ports to :20559 and :20558;
  3. receives incoming HTTP requests and extracts the hostname (eg: myapp.test);
  4. serves static files directly if they exist;
  5. otherwise spawns a Rack applications (found at ~/.prax/myapp) if any;
  6. and proxies the request to the Rack aplication or a specified port for port forwarding.

Domain Resolver


If your distribution uses systemd-resolved, just use the .localhost TLD instead of .test —be prepared to fight against systemd if you want to use another TLD, or consider switching to a systemd free Linux.

.test TLD

Prax proposes 2 solutions to resolve .test and .localhost domains:

Prax supports domains, so you can use for example. This is useful when using an external device like a smartphone, tablet or another computer to test your websites on.

Custom TLD

If .test or .localhost domains are not your cup of tea, no problem! Prax will route requests from any TLD to the applications in your ~/.prax directory, as long as the domain resolves to localhost.

For instance, if you wished to visit instead of myapp.test, you could create dnsmasq configuration to resolve .dev domains to localhost, too:

$ sudo tee /etc/dnsmasq.d/dev <<EOF
$ sudo service dnsmasq restart

Port Redirections

The port redirections are iptables rules, that are installed and removed using an initd script. The script redirects the port :80 and :443 on and for each wlanX and ethX devices found on your machine, to allow incoming traffic, so you can use to test on external devices, as mentioned above.

You can install or remove the redirections with:

$ prax iptables [start|stop|restart|status]

Distribution packages should configure an init service to always install the iptables rules on machine startup or before starting prax (warning: this requires root privileges).


Prax is distributed under the CeCILL 2.1 license. Please see LICENSE for details.

HTML templates for rendering errors are from Pow!!, by Sam Stephenson and Basecamp, and are under the MIT license.

The NSSwitch extension originaly come from Hoof, by pyromaniac, and is under the MIT license.


Prax wouldn't exist without Pow!! by Sam Stephenson and Basecamp. Prax is nothing more but a reimplementation (in another language) with Linux compatibility in mind.