Dancer::Config - how to configure Dancer to suit your needs


Dancer::Config handles reading and changing the configuration of your Dancer apps. The documentation for this module aims to describe how to change settings, and which settings are available.


You can change a setting with the keyword set, like the following:

    use Dancer;

    # changing default settings
    set port         => 8080;
    set content_type => 'text/plain';
    set startup_info => 0;

A better way of defining settings exists: using YAML file. For this to be possible, you have to install the YAML module. If a file named config.yml exists in the application directory, it will be loaded, as a setting group.

The same is done for the environment file located in the environments directory.


Run mode and listening interface/port

server (string)

The IP address that the Dancer app should bind to. Default is, i.e. bind to all available interfaces.

port (int)

The port Dancer will listen to.

Default value is 3000. This setting can be changed on the command-line with the --port switch.

daemon (boolean)

If set to true, runs the standalone webserver in the background. This setting can be changed on the command-line with the --daemon flag.

behind_proxy (boolean)

If set to true, Dancer will look to X-Forwarded-Protocol and X-Forwarded-host when constructing URLs (for example, when using redirect. This is useful if your application is behind a proxy.

Content type / character set

content_type (string)

The default content type of outgoing content. Default value is 'text/html'.

charset (string)

This setting has multiple effects:

  • It sets the default charset of outgoing content. charset= item will be added to Content-Type response header.

  • It makes Unicode bodies in HTTP responses of text/* types to be encoded to this charset.

  • It also indicates to Dancer in which charset the static files and templates are encoded.

  • If you're using Dancer::Plugin::Database, UTF-8 support will automatically be enabled for your database - see "AUTOMATIC UTF-8 SUPPORT" in Dancer::Plugin::Database

Default value is empty which means don't do anything. HTTP responses without charset will be interpreted as ISO-8859-1 by most clients.

You can cancel any charset processing by specifying your own charset in Content-Type header or by ensuring that response body leaves your handler without Unicode flag set (by encoding it into some 8bit charset, for example).

Also, since automatically serialized JSON responses have application/json Content-Type, you should always encode them by hand.

default_mime_type (string)

Dancer's Dancer::MIME module uses application/data as a default mime type. This setting lets the user change it. For example, if you have a lot of files being served in the public folder that do not have an extension, and are text files, set the default_mime_type to text/plain.

File / directory locations

environment (string)

This is the name of the environment that should be used. Standard Dancer applications have a environments folder with specific configuration files for different environments (usually development and production environments). They specify different kind of error reporting, deployment details, etc. These files are read after the generic config.yml configuration file.

The running environment can be set with:

   set environment => "production";

Note that this variable is also used as a default value if other values are not defined.

appdir (directory)

This is the path where your application will live. It's where Dancer will look by default for your config files, templates and static content.

It is typically set by use Dancer to use the same directory as your script.

public (directory)

This is the directory, where static files are stored. Any existing file in that directory will be served as a static file, before matching any route.

By default, it points to $appdir/public.

views (directory)

This is the directory where your templates and layouts live. It's the "view" part of MVC (model, view, controller).

This defaults to $appdir/views.

Templating & layouts


Allows you to configure which template engine should be used. For instance, to use Template Toolkit, add the following to config.yml:

    template: template_toolkit

layout (string)

The name of the layout to use when rendering view. Dancer will look for a matching template in the directory $views/layout.

Your can override the default layout using the third argument of the template keyword. Check Dancer manpage for details.

Logging, debugging and error handling

strict_config (boolean, default: false)

If true, config will return an object instead of a hash reference. See Dancer::Config::Object for more information.

global_warnings (boolean, default: false)

If true, use warnings will be in effect for all modules and scripts loaded by your Dancer application. Set to a true value to enable this.

startup_info (boolean)

If set to true, prints a banner at the server start with information such as versions and the environment (or "dancerfloor").

Conforms to the environment variable DANCER_STARTUP_INFO.

warnings (boolean)

If set to true, tells Dancer to consider all warnings as blocking errors.

traces (boolean)

If set to true, Dancer will display full stack traces when a warning or a die occurs. (Internally sets Carp::Verbose). Default to false.

server_tokens (boolean)

If set to true, Dancer will add an "X-Powered-By" header and also append the Dancer version to the "Server" header. Default to true.

You can also use the environment variable DANCER_SERVER_TOKENS.

log_path (string)

Folder where the ``file logger'' saves logfiles.

log_file (string)

Name of the file to create when ``file logger'' is active. It defaults to the environment setting contents.

logger (enum)

Select which logger to use. For example, to write to log files in log_path:

    logger: file

Or to direct log messages to the console from which you started your Dancer app in standalone mode,

    logger: console

Various other logger backends are available on CPAN, including Dancer::Logger::Syslog, Dancer::Logger::Log4perl, Dancer::Logger::PSGI (which can, with the aid of Plack middlewares, send log messages to a browser's console window) and others.

log (enum)

Tells which log messages should be actually logged. Possible values are core, debug, warning or error.

core : all messages are logged, including some from Dancer itself
debug : all messages are logged
info : only info, warning and error messages are logged
warning : only warning and error messages are logged
error : only error messages are logged

During development, you'll probably want to use debug to see your own debug messages, and core if you need to see what Dancer is doing. In production, you'll likely want error or warning only, for less-chatty logs.

show_errors (boolean)

If set to true, Dancer will render a detailed debug screen whenever an error is caught. If set to false, Dancer will render the default error page, using $public/$error_code.html if it exists or the template specified by the error_template setting.

The error screen attempts to sanitise sensitive looking information (passwords / card numbers in the request, etc) but you still should not have show_errors enabled whilst in production, as there is still a risk of divulging details.

error_template (template path)

This setting lets you specify a template to be used in case of runtime error. At the present moment the template can use three variables:


The error title.


The error message.


The code throwing that error.

auto_reload (boolean)

Requires Module::Refresh and Clone.

If set to true, Dancer will reload the route handlers whenever the file where they are defined is changed. This is very useful in development environment but should not be enabled in production. Enabling this flag in production yields a major negative effect on performance because of Module::Refresh.

When this flag is set, you don't have to restart your webserver whenever you make a change in a route handler.

Note that Module::Refresh only operates on files in %INC, so if the script your Dancer app is started from changes, even with auto_reload enabled, you will still not see the changes reflected until you start your app.

Session engine

session (enum)

This setting lets you enable a session engine for your web application. Be default, sessions are disabled in Dancer, you must choose a session engine to use them.

See Dancer::Session for supported engines and their respective configuration.


The session expiry time in seconds, or as e.g. "2 hours" (see "expires" in Dancer::Cookie. By default, there is no specific expiry time.


The name of the cookie to store the session ID in. Defaults to dancer.session. This can be overridden by certain session engines.


The user's session ID is stored in a cookie. If the session_secure setting is set to a true value, the cookie will be marked as secure, meaning it should only be sent over HTTPS connections.


This setting defaults to 1 and instructs the session cookie to be created with the HttpOnly option active, meaning that JavaScript will not be able to access to its value.


Allows you to set the domain property on the cookie, which will override the default. This is useful for setting the session cookie's domain to something like so that the same cookie will be applicable and usable across subdomains of a base domain.

auto_page (boolean)

For simple pages where you're not doing anything dynamic, but still want to use the template engine to provide headers etc, you can use the auto_page feature to avoid the need to create a route for each page.

With auto_page enabled, if the requested path does not match any specific route, Dancer will check in the views directory for a matching template, and use it to satisfy the request if found.

Simply enable auto_page in your config:

    auto_page: 1

Then, if you request /foo/bar, Dancer will look in the views dir for /foo/

Dancer will honor your before_template_render code, and all default variables. They will be accessible and interpolated on automatic served pages.

The pages served this way will have Content-Type set to text/html, so don't use the feature for anything else.

Route caching

route_cache (boolean)

Enables route caching (for quicker route resolution on larger apps - not caching of responses). See Dancer::Route::Cache for details.

route_cache_size_limit (bytes)

Maximum size of route cache (e.g. 1024, 2M) - see Dancer::Route::Cache

route_cache_path_limit (number)

Maximum number of routes to cache - see Dancer::Route::Cache


It's possible to set the configuration directory and environment directory using this two environment variables. Setting `DANCER_CONFDIR` will have the same effect as doing

    set confdir => '/path/to/confdir'

and setting `DANCER_ENVDIR` will be similar to:

    set envdir => '/path/to/environments'


This module has been written by Alexis Sukrieh <> and others, see the AUTHORS file that comes with this distribution for details.


This module is free software and is released under the same terms as Perl itself.