Facebook App: localhost no longer works as app domain

The protocol seems to keep changing, and the accepted answer didn't work for me today. In case it helps other searchers, this is what did work for me:

• All changes were made on the Settings page under the Basic tab

1.) In the center under the first box of options, click "+ Add Platform" and choose "Website" (or whatever is appropriate for your app.)

2.) In the box that comes up for the website you just added: Site URL: http://localhost:3000/

3.) In the box above that (Settings => Basic): App Domain: localhost

4.) At the bottom right - click "Save Changes"

5.) Make sure you have the app ID copied and pasted correctly into your code. (The ID is in the first box on that page if you need it again.)

1. Go to your App's settings page in http://developers.facebook.com
2. Click on the dropdown arrow on the top left (next to the name of your app) and click "Create Test App" and give it a name
3. In the Settings > Basic of that new Test App set the App Domains as "localhost"
4. Also set the Website Site URL as "http://localhost:8888" (or whatever port you are using).
5. IMPORTANT: this app has different App ID and App Secret from your online application. So, last step: make sure that you update the code that sits in your localhost with the Test App's App ID and App Secret. On the contrary, the code that sits in the live server should be using the main App's ID and Secret.

You can still test your app without deploying it on a remote sever like heroku.The trick is to update the etc/hosts file this way:

127.0.0.1 mydomain.com

Then on the Facebook App's settings, type [http://] mydomain.com, without the "[" and "]"

It worked for me this way