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"Route" module

The Route module allows you to work with URLs in a type-safe way. You can directly access fields like route.path, route.query, or route.params without needing to parse the URL by hand.

It also comes with some helpful functions for working with <a href></a> tags in HTML, or converting to a URL for other use cases like error reporting.


Here is the complete definition of the Route type:

type alias Route params =
    { path : Route.Path.Path
    , params : params
    , query : Dict String String
    , hash : Maybe String
    , url : Url

The Route type is a record with fields that are commonly used when building web applications. The following sections break down when you might want to use each field.


Each item in the Route.Path module has a one-to-one mapping with a file in the src/Pages folder. Comparing two path values is often a good way to know if you are on the same page or not.

For example, if we were on the homepage, then route.path == Route.Path.Home_. If our application had a "Settings" page, then this value would be route.path == Route.Path.Settings.

Keep in mind that all values in Route.Path are generated based on the names of files in the src/Pages folder. Deleting a page file will automatically remove a Route.Path value.


The Route params type will have parameters based on what page you are working in. Shared modules, layouts, and static page routes will all have Route () by default. This denotes there are no dynamic variables you can access.

Pages with Dynamic routes might have a value like Route { id : String }, depending on the name of the dynamic page file.


Many applications use a specific format for query parameters that looks somethings like this:


To make it easy to access those key value pairs, Elm Land created the route.query type. It uses a Dict to make looking up values easier for your application code:

-- ?sort=name&owner=me&date=upcoming

Dict.get "sort" route.query == Just "name"
Dict.get "owner" route.query == Just "me"
Dict.get "date" route.query == Just "upcoming"
Dict.get "archived" route.query == Nothing


It's common to use #section-name when making applications that have jump links (like this documentation site). The route.hash value will give you back the current value of the hash or URL fragment (if it exists).


If you ever need access to the standard elm/url value, it is available in route.url. Sometimes this is useful if you need to know the protocol, current port, hostname, or access the raw query parameter strings.


This is a helpful function when rendering HTML <a> tags.

Rather than working with String URLs in your code, we recommend using either Route.Path.href or Route.href. When you delete a page, the Elm compiler can walk you through any broken links in your application. Using the standard Html.Attributes.href doesn't have that guarantee.

Route.href : 
    { path : Route.Path.Path
    , query : Dict String String
    , hash : Maybe String
    -> Html.Attribute msg

Tip: If you don't care about query or hash, prefer to use Route.Path.href instead!


In rare cases, like error reporting, you may find a need to convert a Route value into a URL string. That string will include the query parameters, hash fragment, and URL path.

This can also be helpful when working with Elm UI, Elm CSS, or anything that isn't elm/html values.

Route.toString :
    { route
        | path : Route.Path.Path
        , query : Dict String String
        , hash : Maybe String
    -> String

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