Create routes

You may want to make prototypes that are more complex than simple HTML files. For example, you may want to respond to input from a form and show different pages based on answers given by the user (also called branching).

To do this you will need to create 'routes' - rules for the Prototype Kit to respond to certain web addresses (URLs), in the file app/routes.js

Requests and responses

Diagram showing a browser on a laptop with an arrow labelled 'request' going to a server. An arrow labelled 'response' comes back to the laptop.

When you enter http://localhost:3000/start in a browser, the browser sends a request to the server - the Prototype Kit. The kit processes that request and sends a response.

The kit looks in the app/views folder for a file called start.html. It adds the GOV.UK header and footer, and sends the whole start page back as a response to the browser.

If the kit cannot find start.html in app/views, it will send an 'Error: not found' page instead.


You can control the response to any request by adding routes to the app/routes.js file. Routes are written in JavaScript.

This is an example of a route:'/live-in-uk-answer', function(request, response) {

    var liveInUK =['live-in-uk']
    if (liveInUK == "Yes"){
    } else {

In this example, the user was asked if they live in the UK, with 'Yes' and 'No' radio buttons to answer.

This route sends the user to a different page depending on their answer.

Let's look at each bit of this route code separately.

The router handles all the requests. There are 2 ways a browser can make a request: 'get' and 'post'.

  • a get request is when you enter an address in the browser or follow a link
  • a post request is when you submit your answer to a form with a button

This route will only run when the request is post, not get.


This is called the request path. On the question page, the form has an action with the same path.

function(request, response)

This is our function (piece of code) to process the request. It has access to 2 variables (pieces of data):

  • request - contains information from the browser, including the user's answers
  • response - lets us send instructions to the browser, for example the next page to redirect to

var liveInUK =['live-in-uk']

To send users to different pages based on their answers, the kit stores all answers in a variable called

We need the answer to 'Do you live in the UK?' ['live-in-uk']

We use var liveInUK = to copy['live-in-uk'] to a shorter variable. This makes it easier to type later on.

if (liveInUK == "Yes"){

This code checks whether the answer to 'Do you live in the UK' is 'Yes'.

Note the double = symbol for checking an answer. A single = makes a copy as we did above.


Because the user's answer is 'Yes', our response is to redirect them to /next-question - as they are eligible to use the service.

} else {

If the user's answer was not 'Yes', we use else to set a different response.


Our response is to redirect them to /ineligible - they are not eligible to continue in the service.

Find out how to make branching journeys using routes.

Advanced documentation for routes.