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


version 1.3521


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.

To fetch the available configuration values use the config keyword that returns a reference to a hash:

    my $port   = config->{port};
    my $appdir = config->{appdir};

By default, the module YAML will be used to parse the configuration files. If desired, it is possible to use YAML::XS instead by changing the YAML engine configuration in the application code:

    config->{engines}{YAML}{module} = 'YAML::XS';

See Dancer::Serializer::YAML for more details.


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.

Can also be set with environment variable DANCER_SERVER

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.

Can also be set with environment variable DANCER_PORT

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.

Can also be enabled by setting environment variable DANCER_DAEMON to a true value.

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.

It will also cause Dancer::Request->address to return what Dancer::Request->forwarded_for_address would return, namely the content of the `HTTP_X_FORWARDED_FOR` env var/header, so that requests will appear to have come from the end user's IP and not the proxy's.

Because of the above, you should *not* turn this on if your app isn't behind a proxy which will pass this information on appropriately, otherwise a malicious user could supply false information.

Content type / character set

content_type (string)

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

Can also be set with environment variable DANCER_CONTENT_TYPE

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.

Can also be set with environment variable DANCER_CHARSET

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 an environments folder with specific configuration files for different environments (usually development and production environments). They specify different kinds 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.

Can also be set with environment variable DANCER_ENVIRONMENT

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.

Can also be set with environment variable DANCER_APPDIR

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/layouts.

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. Default is false.

Can also be enabled by setting the environment variable DANCER_WARNINGS to a true value.

startup_info (boolean)

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

Can also be disabled by setting the environment variable DANCER_NO_STARTUP_INFO to a true value.

warnings (boolean)

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

traces (boolean)

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

Can also be enabled by setting environment variable DANCER_TRACES to a true value.

require_environment (boolean)

If set to true, Dancer will fail during startup if your environment file is missing or can't be read. This is especially useful in production when you have things like memcached settings that need to be set per-environment. Defaults to false.

server_tokens (boolean)

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

Can also be disabled by setting the environment variable DANCER_NO_SERVER_TOKENS to a true value.

log_path (string)

Folder where the ``file logger'' saves log files.

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.

Can also be set with environment variable DANCER_LOGGER

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.

Session engine

session (enum)

This setting lets you enable a session engine for your web application. By 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 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.


If set, session cookies will have the SameSite attribute set to the specified value to control cross-site request cookie handling. If set, the value must be one of the values described in RFC6265bis - 'Strict', 'Lax' or 'None'.

Strict - Cookies will only be sent in a first-party context and not be sent along with requests initiated by third party websites.
Lax - Cookies are allowed to be sent with top-level navigations and will be sent along with GET request initiated by third party website. This is the default value in modern browsers.
None - Cookies will be sent in all contexts, i.e sending cross-origin is allowed.

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 automaticly-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)

If true, enables route caching (for quicker route resolution on larger apps - not caching of responses). See Dancer::Route::Cache for details. Default is false.

route_cache_size_limit (bytes)

Maximum size of route cache (e.g. 1024, 2M). Defaults to 10M (10MB) - see Dancer::Route::Cache

route_cache_path_limit (number)

Maximum number of routes to cache. Defaults to 600 - see Dancer::Route::Cache


It's possible to set the configuration directory and environment directory using these 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'


Some settings can be provided via environment variables at runtime, as detailed above; a full list of environment variables you can use follows.


DANCER_APPHANDLER a Dancer::Handler::* by default Dancer::Handler::Standalone
















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.




Dancer Core Developers


This software is copyright (c) 2010 by Alexis Sukrieh.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.