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Application: side-by-side-browser

Proxy a web site to preview the redirections ahead of it being transitioned to GOV.UK


The production version of this application is hosted on Heroku.


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Proxy a web site to preview redirections ahead of it being transitioned to GOV.UK.

sketchy explanation

Run the tests

$ npm install
$ npm test


$ node server.js

...then you can use to make it work with localhost, eg:


Run the server on Heroku. It requires a side-by-side wildcard subdomain pointed to it:

$ heroku domains:add *

Follow the returned instructions to CNAME the wildcard to Heroku.

By default, the application will take its list of allowed domains from the production instance of the GOV.UK Transition tool. This can be overridden with the SIDE_BY_SIDE_HOSTS environment variable. Examples:

  • SIDE_BY_SIDE_HOSTS= (the default)
  • SIDE_BY_SIDE_HOSTS=file:etc/hosts.json