Dancer2::Config(3) Configure Dancer2 to suit your needs


version 0.200002


The Dancer2 configuration (as implemented by Dancer2::Core::Role::ConfigReader) handles reading and changing the configuration of your Dancer2 apps. This document describes how to manipulate Dancer2's configuration settings (through code or by file), and to document the various settings that are available in Dancer2.


You can change a setting with the keyword "set":

    use Dancer2;
    # changing default settings
    set port         => 8080;
    set content_type => 'text/plain';
    set startup_info => 0;


There's nothing wrong with using "set" to configure your application. In fact you might have some great reasons for doing so. For greater flexibility, ease of deployment, etc., you should also consider extracting those settings into a configuration file.

Configuration file path and file names

Dancer2 will first look for the file config.ext (where .ext is the type of configuration file you are using) in the root directory of your application. This is considered your global Dancer2 config file. If you do not care to have separate settings for production and development environments (not a recommended practice!), then this file is all you need.

Next, Dancer2 will look in the environments directory for a configuration file specific to the platform you are deploying to (production.ext and development.ext, for example). Any settings in these files that are named the same as settings in your global configuration file will take precedence over those settings in the global file. The rest of the settings are merged and Dancer2 uses the combination of settings from the two files as its operating configuration.

Supported configuration file formats

Dancer2 supports any configuration file format that is supported by Config::Any. At the time of this writing, that includes YAML (.yml and .yaml), JSON (.jsn and .json), INI (.ini), Apache-style configurations (.cnf and .conf), XML (.xml), and Perl-style hashes (.pl and .perl).

Make sure you pick the appropriate extension for your configuration file name, as Dancer2 guesses the type of format based on the file extension.

Sample configuration files

Note: Not all possibilities are covered here, only the most common options.

If you prefer YAML, a sample YAML based config file might look like this:

    appname: "Hello"
    charset: "UTF-8"
    auto_page: 1
    session: "YAML"
    serializer: "JSON"
          dsn: dbi:SQLite:db/mydata.db
          schema_class: Hello::Schema

If JSON is more your thing, your file might look more like this:

        "appname": "Hello",
        "charset": "UTF-8",
        "auto_page": "1",
        "session": "YAML",
        "serializer": "JSON",
        "plugins": {
            "DBIC": {
                "default": {
                    "dsn": "dbi:SQLite:db/mydata.db",
                    "schema_class": "Hello::Schema"

If you like Apache configuration files, try something similar to:

        appname = Hello
        charset = UTF-8
        auto_page = 1
        session = YAML
        serializer = JSON
                    dsn = dbi =SQLite =db/mydata.db
                    schema_class = Hello = =Schema

INI-style files are deliberately simplistic and not recommended for use in your Dancer2 applications.


Run mode and listening interface/port

server (string)

The IP address that the Dancer2 app should bind to. Default is, i.e. bind to all available interfaces.

port (int)

The port Dancer2 will listen to.

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

behind_proxy (boolean)

If set to true, Dancer2 will look to "X-Forwarded-Protocol" and "X-Forwarded-host" when constructing URLs (for example, when using "redirect" or "host"). This is useful if your application is behind a proxy.

Note: If either of these are missing, the values of the proxy server will be used instead. For example, if the client sends a HTTP/1.0 request to a proxy that is hosted locally, then "host" will return the value ``localhost''. In a similar vein, if the client makes a secure connection to the proxy, but the proxy does not pass "X-Forwarded-Protocol", then "base" will return ``http://...''. For these reasons, it is recommended that the values are hard-configured in the proxy if possible. For Apache this would be:

    RequestHeader set X_FORWARDED_PROTO "https"
    RequestHeader set X_FORWARDED_HOST ""

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 Dancer2 in which charset the static files and templates are encoded.
  • If you're using Dancer2::Plugin::Database, UTF-8 support will automatically be enabled for your database - see ``AUTOMATIC UTF-8 SUPPORT'' in Dancer2::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)

Dancer2's Dancer2::Core::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 Dancer2 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 Dancer2 will look by default for your config files, templates and static content.

It is typically set by "use Dancer2" to use the same directory as your script.

public_dir (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.

See also static_handler.

Default: "$appdir/public".

static_handler (boolean)

This setting have to be declared and set to true if you modify standard "public_dir" location.

Default: true if $ENV{DANCER_PUBLIC} is set or "public_dir" is set to "$appdir/public".

views (directory)

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

Default: "$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. Dancer2 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 "Dancer2" manpage for details.

layout_dir (string)

A relative path where the layouts reside inside the "views" directory.

    layout_dir: actual_layouts

Default: layouts.

Logging, debugging and error handling

strict_config (boolean, default: false)

If true, "config" will return an object instead of a hash reference. See Dancer2::Config::Object for more information.

startup_info (boolean)

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

Conforms to the environment variable "DANCER_STARTUP_INFO".

traces (boolean)

If set to true, Dancer2 will display full stack traces when a warning or a die occurs. (Internally sets Carp::Verbose). Default to false.

no_server_tokens (boolean)

If set to true, Dancer2 will not add an ``X-Powered-By'' header and also append the Dancer2 version to the ``Server'' header. Default to false - adding.

You can also use the environment variable "DANCER_NO_SERVER_TOKENS".

logger (enum)

Select which logger to use. For example, to write to log files with Dancer2::Logger::File:

    logger: File

Or to direct log messages to the console from which you started your Dancer2 app with Dancer2::Logger::Console:

    logger: Console

Loggers are configured with a corresponding ``Logger engine'' section, as shown below.

session (enum)

This setting lets you enable a session engine for your web application. By default, sessions are disabled in Dancer2, you must choose a session engine to use them.

Sessions are configured with a corresponding ``Session engine'' section, as shown below.

show_errors (boolean)

If set to true, Dancer2 will render a detailed debug screen whenever an error is caught. If set to false, Dancer2 will render the default error page, using "$public/$error_code.html" if it exists, "$views/$" 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 (as well as "$views/$" templates) can use four variables:

The error title.
The error specific content (if any).
The HTTP status code throwing that error.
The stringified exception (e.g. $@) if any.

Keep in mind that 'content' and 'exception' can vary depending on the problem.

For example:

A 404 has an empty 'exception' and 'content' contains the URI that was not found. Unless you do the 404 yourself via "send_error("You chose ... poorly!", 404);", then 'content' is 'You chose ... poorly!'.

A 500 because of, say, dividing 0 by 0 will have an empty 'content' and 'exception like 'Illegal division by zero at ...'.

A 401 from "send_error("You can not know the secret until you sign in grasshopper!", 401);" will have an empty 'exception' and 'content' will contain 'You can not know the secret until you sign in grasshopper!'.

Logger engine

The logger must be configured in a separate "engines" section, like so:

   logger: Console
         log_level: core

All loggers support the configuration options below. See documentation for a particular logger for other supported options.


This option tells which log messages should be actually logged. Possible values are core, info, debug, warning or error.

core : all messages are logged, including some from Dancer2 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 Dancer2 is doing. In production, you'll likely want "error" or "warning" only, for less-chatty logs.

Session engine

The session engine is configured in the "engines" section.

   session: Simple
         cookie_name: dance.set
         cookie_duration: '24 hours'
         is_secure: 1
         is_http_only: 1

See Dancer2::Core::Role::SessionFactory for more detailed documentation for these options, or the particular session engine for other supported options.


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


The domain of the cookie. By default there is no domain defined for the cookie.


The path of the cookie. By default there is no path defined for the cookie.


The session expiry time in seconds, or as e.g. ``2 hours'' (see ``expires'' in Dancer2::Core::Cookie. By default, there is no specific expiry time.


The user's session ID is stored in a cookie. If the "is_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.

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, Dancer2 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", Dancer2 will look in the views dir for "/foo/".

Dancer2 will honor your "before_template_render" code, and all default variables. They will be accessible and interpolated on automatic served pages.


For complex applications that require extended DSL keywords or other functionality the DSL class used can be specified at import time or in the config settings.

    dsl_class: 'My::DSL'

This is the same as specifying

    use Dancer2 dsl => 'My::DSL'

in your module. dsl_class defaults to Dancer2::Core::DSL if not specified

Environment variables


Sets the configuration directory.

This correlates to the "confdir" config option.


Sets the environment directory.

This correlates to the "envdir" config option.


Sets the given environment. This can be overridden by "DANCER_ENVIRONMENT".


Sets the given environment. This takes higher precedence over "PLACK_ENV".

If neither "PLACK_ENV" or "DANCER_ENVIRONMENT" is set, the environment defaults to development.


The "DANCER_APPHANDLER" configuration controls what the "dance" keyword does.

If is set to "PSGI" (which will automatically be set if "PLACK_ENV" is set), "dance" will return the PSGI application coderef.

Otherwise (which is the default is - "Standalone"), it runs the Plack standalone server with the application.


Sets the port which will be used by the development server (if not run by plackup).


Sets the host the development server will be used by the development server (if not run by plackup).

Note: this might change in the future.


Controls whether to display start up info.


Controls whether to display the server tokens.


Sets the public directory location.


Sets the tracing flag which sets Carp's $Verbose flag.


Sets the views (templates) directory.


Sets the logger engine.


Sets the default charset.


Sets the default content type.

If not set, defaults to text/html.


Dancer Core Developers


This software is copyright (c) 2016 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.