Squash automatically adds a comment on each Pull Request with a unique URL per branch of code.
When you click on such URLs Squash will create a new virtual machine and will immediately display a loading page like this:
and then it will start deploying your branch’s code. When your application build process is finished, Squash will look for a success response and will then automatically start routing requests to your application. When that happens your application will start working off the same URL:
Multiple applications and multiple PR links
You can also customize the comments to allow listing multiple applications and subdomains.