Rack proxy server for development (Crystal port)
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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 domains to / ::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. spawns a Rack applications (found at ~/.prax/myapp) if any
  5. proxies the request to the spawned Rack aplication or to the specified port.

.test TLD

Prax proposes 2 solutions to resolve .test domains:

  • a dnsmasq configuration, either throught NetworkManager or by installing dnsmasq manually (eg. through your Linux distribution package);
  • an obsolete and deprecated NSSwitch extension, only compatible wih glibc and no longer compatible with Google Chrome/Chromium, and certainly more;

Prax also supports http://xip.io domains, so you may use myapp. for example. This is very useful when using an external device like a smartphone or tablet or another computer.

If your computer runs systemd, it's possible a service such as systemd-networkd or systemd-resolved or something else systemd took over, is conflicting with a local resolver. I don't have a solution —except to stay as far away as possible from systemd as possible.

Other TLDs

If .test 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 "myapp.dev" 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 may use xip.io to test on external devices, as mentioned above.


In Chrome, if one types "myapp.test" into the URL bar, Chrome will issue a search. Type "http://myapp.test" or "myapp.test/" instead to visit that URL.


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.