1. To check which version of the website you are viewing, put some flag on the test site (something like “test” somewhere on the screen).

2. Open hosts file for editing:

sudo nano /etc/hosts

3. Add this line at the bottom:

Add this at the bottom of the file:

[Ip address] [domain name]

For example: www.mydomain.com

Save the file.

4. Flush the DNS cache on your computer

dscacheutil -flushcache

5. Close the browser application and reopen it. (In most cases just a hard refresh would be sufficient).

Alternatively, you can use Gas Mask on Mac. Click on the GasMask icon near the upper right corner of your computer’s utilities bar, select “Open Editor Window”, add the IP address and domain name, as described above, and click the Save button (looks like the dot in the center of the button].


NOTE: one additional action recommended by another resource: sudo killall -HUP mDNSResponder 

Reference: https://www.imore.com/how-edit-your-macs-hosts-file-and-why-you-would-want