← Back to all posts

How to set up a subdomain on Rails localhost

David Anderson | Apr 20, 2019

I recently worked on a client project that required setting up a subdomain for each of the client’s customers. For example, they wanted to use company1.everclimb.co for Company 1 and company2.everclimb.co for Company 2. Though the app was essentially the same for both Company 1 and Company 2 there were a few things that changed based upon the subdomain, such as displaying the appropriate company’s logo in the nav bar. I managed to test this locally by editing my hosts file.

You can find your hosts file here: /private/etc/hosts Because the file is locked, I had to find the File using Finder, move it to the desktop, edit it, save it, and then move it back to /private/etc/

Finder --> Go --> Go to folder --> /private/etc/hosts

Move the file to your Desktop and open it using your text editor. You can add something like:       abcwidgets.local.host

Save the file and move it back into /private/etc. Navigate to your rails app and run the server rails s. Assuming you’re running on the default port (3000), you should now be able to access the subdomain at


Good luck!


Drop your email in the box below to subscribe to my newsletter. Once per week you'll get Ruby/Rails tips, guides, job postings, and general thoughts from the web developer trenches.