Insightly Classic is the old version of Insightly. It's not available to new accounts. Users on Insightly Classic can switch over to the latest version.
An Insightly URL is a unique web address you can create for your users to bookmark and sign in from. This replaces the auto-generated URL that may be hard to remember.
The last part of your custom URL is always .insight.ly but you can change the first part to something your users will remember, like http://mycompany.insight.ly.
Go to System Settings > Insightly URL to set it up.
Your Insightly URL must contain only the characters A-Z or a-z, the numbers 0-9, or the hyphen character. No spaces are allowed and it must include at least 5 characters. You can use any name that hasn't already been reserved.
If you use Insightly for G Suite, you will need to log in through Google instead of this URL.
If you later change your Insightly URL, be sure to share it with your users so they can continue to access Insightly.